diff --git a/vendor/google.golang.org/protobuf/internal/impl/convert.go b/vendor/google.golang.org/protobuf/internal/impl/convert.go
new file mode 100644
index 0000000..acd61bb
--- /dev/null
+++ b/vendor/google.golang.org/protobuf/internal/impl/convert.go
@@ -0,0 +1,496 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package impl
+
+import (
+	"fmt"
+	"reflect"
+
+	pref "google.golang.org/protobuf/reflect/protoreflect"
+)
+
+// unwrapper unwraps the value to the underlying value.
+// This is implemented by List and Map.
+type unwrapper interface {
+	protoUnwrap() interface{}
+}
+
+// A Converter coverts to/from Go reflect.Value types and protobuf protoreflect.Value types.
+type Converter interface {
+	// PBValueOf converts a reflect.Value to a protoreflect.Value.
+	PBValueOf(reflect.Value) pref.Value
+
+	// GoValueOf converts a protoreflect.Value to a reflect.Value.
+	GoValueOf(pref.Value) reflect.Value
+
+	// IsValidPB returns whether a protoreflect.Value is compatible with this type.
+	IsValidPB(pref.Value) bool
+
+	// IsValidGo returns whether a reflect.Value is compatible with this type.
+	IsValidGo(reflect.Value) bool
+
+	// New returns a new field value.
+	// For scalars, it returns the default value of the field.
+	// For composite types, it returns a new mutable value.
+	New() pref.Value
+
+	// Zero returns a new field value.
+	// For scalars, it returns the default value of the field.
+	// For composite types, it returns an immutable, empty value.
+	Zero() pref.Value
+}
+
+// NewConverter matches a Go type with a protobuf field and returns a Converter
+// that converts between the two. Enums must be a named int32 kind that
+// implements protoreflect.Enum, and messages must be pointer to a named
+// struct type that implements protoreflect.ProtoMessage.
+//
+// This matcher deliberately supports a wider range of Go types than what
+// protoc-gen-go historically generated to be able to automatically wrap some
+// v1 messages generated by other forks of protoc-gen-go.
+func NewConverter(t reflect.Type, fd pref.FieldDescriptor) Converter {
+	switch {
+	case fd.IsList():
+		return newListConverter(t, fd)
+	case fd.IsMap():
+		return newMapConverter(t, fd)
+	default:
+		return newSingularConverter(t, fd)
+	}
+	panic(fmt.Sprintf("invalid Go type %v for field %v", t, fd.FullName()))
+}
+
+var (
+	boolType    = reflect.TypeOf(bool(false))
+	int32Type   = reflect.TypeOf(int32(0))
+	int64Type   = reflect.TypeOf(int64(0))
+	uint32Type  = reflect.TypeOf(uint32(0))
+	uint64Type  = reflect.TypeOf(uint64(0))
+	float32Type = reflect.TypeOf(float32(0))
+	float64Type = reflect.TypeOf(float64(0))
+	stringType  = reflect.TypeOf(string(""))
+	bytesType   = reflect.TypeOf([]byte(nil))
+	byteType    = reflect.TypeOf(byte(0))
+)
+
+var (
+	boolZero    = pref.ValueOfBool(false)
+	int32Zero   = pref.ValueOfInt32(0)
+	int64Zero   = pref.ValueOfInt64(0)
+	uint32Zero  = pref.ValueOfUint32(0)
+	uint64Zero  = pref.ValueOfUint64(0)
+	float32Zero = pref.ValueOfFloat32(0)
+	float64Zero = pref.ValueOfFloat64(0)
+	stringZero  = pref.ValueOfString("")
+	bytesZero   = pref.ValueOfBytes(nil)
+)
+
+func newSingularConverter(t reflect.Type, fd pref.FieldDescriptor) Converter {
+	defVal := func(fd pref.FieldDescriptor, zero pref.Value) pref.Value {
+		if fd.Cardinality() == pref.Repeated {
+			// Default isn't defined for repeated fields.
+			return zero
+		}
+		return fd.Default()
+	}
+	switch fd.Kind() {
+	case pref.BoolKind:
+		if t.Kind() == reflect.Bool {
+			return &boolConverter{t, defVal(fd, boolZero)}
+		}
+	case pref.Int32Kind, pref.Sint32Kind, pref.Sfixed32Kind:
+		if t.Kind() == reflect.Int32 {
+			return &int32Converter{t, defVal(fd, int32Zero)}
+		}
+	case pref.Int64Kind, pref.Sint64Kind, pref.Sfixed64Kind:
+		if t.Kind() == reflect.Int64 {
+			return &int64Converter{t, defVal(fd, int64Zero)}
+		}
+	case pref.Uint32Kind, pref.Fixed32Kind:
+		if t.Kind() == reflect.Uint32 {
+			return &uint32Converter{t, defVal(fd, uint32Zero)}
+		}
+	case pref.Uint64Kind, pref.Fixed64Kind:
+		if t.Kind() == reflect.Uint64 {
+			return &uint64Converter{t, defVal(fd, uint64Zero)}
+		}
+	case pref.FloatKind:
+		if t.Kind() == reflect.Float32 {
+			return &float32Converter{t, defVal(fd, float32Zero)}
+		}
+	case pref.DoubleKind:
+		if t.Kind() == reflect.Float64 {
+			return &float64Converter{t, defVal(fd, float64Zero)}
+		}
+	case pref.StringKind:
+		if t.Kind() == reflect.String || (t.Kind() == reflect.Slice && t.Elem() == byteType) {
+			return &stringConverter{t, defVal(fd, stringZero)}
+		}
+	case pref.BytesKind:
+		if t.Kind() == reflect.String || (t.Kind() == reflect.Slice && t.Elem() == byteType) {
+			return &bytesConverter{t, defVal(fd, bytesZero)}
+		}
+	case pref.EnumKind:
+		// Handle enums, which must be a named int32 type.
+		if t.Kind() == reflect.Int32 {
+			return newEnumConverter(t, fd)
+		}
+	case pref.MessageKind, pref.GroupKind:
+		return newMessageConverter(t)
+	}
+	panic(fmt.Sprintf("invalid Go type %v for field %v", t, fd.FullName()))
+}
+
+type boolConverter struct {
+	goType reflect.Type
+	def    pref.Value
+}
+
+func (c *boolConverter) PBValueOf(v reflect.Value) pref.Value {
+	if v.Type() != c.goType {
+		panic(fmt.Sprintf("invalid type: got %v, want %v", v.Type(), c.goType))
+	}
+	return pref.ValueOfBool(v.Bool())
+}
+func (c *boolConverter) GoValueOf(v pref.Value) reflect.Value {
+	return reflect.ValueOf(v.Bool()).Convert(c.goType)
+}
+func (c *boolConverter) IsValidPB(v pref.Value) bool {
+	_, ok := v.Interface().(bool)
+	return ok
+}
+func (c *boolConverter) IsValidGo(v reflect.Value) bool {
+	return v.IsValid() && v.Type() == c.goType
+}
+func (c *boolConverter) New() pref.Value  { return c.def }
+func (c *boolConverter) Zero() pref.Value { return c.def }
+
+type int32Converter struct {
+	goType reflect.Type
+	def    pref.Value
+}
+
+func (c *int32Converter) PBValueOf(v reflect.Value) pref.Value {
+	if v.Type() != c.goType {
+		panic(fmt.Sprintf("invalid type: got %v, want %v", v.Type(), c.goType))
+	}
+	return pref.ValueOfInt32(int32(v.Int()))
+}
+func (c *int32Converter) GoValueOf(v pref.Value) reflect.Value {
+	return reflect.ValueOf(int32(v.Int())).Convert(c.goType)
+}
+func (c *int32Converter) IsValidPB(v pref.Value) bool {
+	_, ok := v.Interface().(int32)
+	return ok
+}
+func (c *int32Converter) IsValidGo(v reflect.Value) bool {
+	return v.IsValid() && v.Type() == c.goType
+}
+func (c *int32Converter) New() pref.Value  { return c.def }
+func (c *int32Converter) Zero() pref.Value { return c.def }
+
+type int64Converter struct {
+	goType reflect.Type
+	def    pref.Value
+}
+
+func (c *int64Converter) PBValueOf(v reflect.Value) pref.Value {
+	if v.Type() != c.goType {
+		panic(fmt.Sprintf("invalid type: got %v, want %v", v.Type(), c.goType))
+	}
+	return pref.ValueOfInt64(int64(v.Int()))
+}
+func (c *int64Converter) GoValueOf(v pref.Value) reflect.Value {
+	return reflect.ValueOf(int64(v.Int())).Convert(c.goType)
+}
+func (c *int64Converter) IsValidPB(v pref.Value) bool {
+	_, ok := v.Interface().(int64)
+	return ok
+}
+func (c *int64Converter) IsValidGo(v reflect.Value) bool {
+	return v.IsValid() && v.Type() == c.goType
+}
+func (c *int64Converter) New() pref.Value  { return c.def }
+func (c *int64Converter) Zero() pref.Value { return c.def }
+
+type uint32Converter struct {
+	goType reflect.Type
+	def    pref.Value
+}
+
+func (c *uint32Converter) PBValueOf(v reflect.Value) pref.Value {
+	if v.Type() != c.goType {
+		panic(fmt.Sprintf("invalid type: got %v, want %v", v.Type(), c.goType))
+	}
+	return pref.ValueOfUint32(uint32(v.Uint()))
+}
+func (c *uint32Converter) GoValueOf(v pref.Value) reflect.Value {
+	return reflect.ValueOf(uint32(v.Uint())).Convert(c.goType)
+}
+func (c *uint32Converter) IsValidPB(v pref.Value) bool {
+	_, ok := v.Interface().(uint32)
+	return ok
+}
+func (c *uint32Converter) IsValidGo(v reflect.Value) bool {
+	return v.IsValid() && v.Type() == c.goType
+}
+func (c *uint32Converter) New() pref.Value  { return c.def }
+func (c *uint32Converter) Zero() pref.Value { return c.def }
+
+type uint64Converter struct {
+	goType reflect.Type
+	def    pref.Value
+}
+
+func (c *uint64Converter) PBValueOf(v reflect.Value) pref.Value {
+	if v.Type() != c.goType {
+		panic(fmt.Sprintf("invalid type: got %v, want %v", v.Type(), c.goType))
+	}
+	return pref.ValueOfUint64(uint64(v.Uint()))
+}
+func (c *uint64Converter) GoValueOf(v pref.Value) reflect.Value {
+	return reflect.ValueOf(uint64(v.Uint())).Convert(c.goType)
+}
+func (c *uint64Converter) IsValidPB(v pref.Value) bool {
+	_, ok := v.Interface().(uint64)
+	return ok
+}
+func (c *uint64Converter) IsValidGo(v reflect.Value) bool {
+	return v.IsValid() && v.Type() == c.goType
+}
+func (c *uint64Converter) New() pref.Value  { return c.def }
+func (c *uint64Converter) Zero() pref.Value { return c.def }
+
+type float32Converter struct {
+	goType reflect.Type
+	def    pref.Value
+}
+
+func (c *float32Converter) PBValueOf(v reflect.Value) pref.Value {
+	if v.Type() != c.goType {
+		panic(fmt.Sprintf("invalid type: got %v, want %v", v.Type(), c.goType))
+	}
+	return pref.ValueOfFloat32(float32(v.Float()))
+}
+func (c *float32Converter) GoValueOf(v pref.Value) reflect.Value {
+	return reflect.ValueOf(float32(v.Float())).Convert(c.goType)
+}
+func (c *float32Converter) IsValidPB(v pref.Value) bool {
+	_, ok := v.Interface().(float32)
+	return ok
+}
+func (c *float32Converter) IsValidGo(v reflect.Value) bool {
+	return v.IsValid() && v.Type() == c.goType
+}
+func (c *float32Converter) New() pref.Value  { return c.def }
+func (c *float32Converter) Zero() pref.Value { return c.def }
+
+type float64Converter struct {
+	goType reflect.Type
+	def    pref.Value
+}
+
+func (c *float64Converter) PBValueOf(v reflect.Value) pref.Value {
+	if v.Type() != c.goType {
+		panic(fmt.Sprintf("invalid type: got %v, want %v", v.Type(), c.goType))
+	}
+	return pref.ValueOfFloat64(float64(v.Float()))
+}
+func (c *float64Converter) GoValueOf(v pref.Value) reflect.Value {
+	return reflect.ValueOf(float64(v.Float())).Convert(c.goType)
+}
+func (c *float64Converter) IsValidPB(v pref.Value) bool {
+	_, ok := v.Interface().(float64)
+	return ok
+}
+func (c *float64Converter) IsValidGo(v reflect.Value) bool {
+	return v.IsValid() && v.Type() == c.goType
+}
+func (c *float64Converter) New() pref.Value  { return c.def }
+func (c *float64Converter) Zero() pref.Value { return c.def }
+
+type stringConverter struct {
+	goType reflect.Type
+	def    pref.Value
+}
+
+func (c *stringConverter) PBValueOf(v reflect.Value) pref.Value {
+	if v.Type() != c.goType {
+		panic(fmt.Sprintf("invalid type: got %v, want %v", v.Type(), c.goType))
+	}
+	return pref.ValueOfString(v.Convert(stringType).String())
+}
+func (c *stringConverter) GoValueOf(v pref.Value) reflect.Value {
+	// pref.Value.String never panics, so we go through an interface
+	// conversion here to check the type.
+	s := v.Interface().(string)
+	if c.goType.Kind() == reflect.Slice && s == "" {
+		return reflect.Zero(c.goType) // ensure empty string is []byte(nil)
+	}
+	return reflect.ValueOf(s).Convert(c.goType)
+}
+func (c *stringConverter) IsValidPB(v pref.Value) bool {
+	_, ok := v.Interface().(string)
+	return ok
+}
+func (c *stringConverter) IsValidGo(v reflect.Value) bool {
+	return v.IsValid() && v.Type() == c.goType
+}
+func (c *stringConverter) New() pref.Value  { return c.def }
+func (c *stringConverter) Zero() pref.Value { return c.def }
+
+type bytesConverter struct {
+	goType reflect.Type
+	def    pref.Value
+}
+
+func (c *bytesConverter) PBValueOf(v reflect.Value) pref.Value {
+	if v.Type() != c.goType {
+		panic(fmt.Sprintf("invalid type: got %v, want %v", v.Type(), c.goType))
+	}
+	if c.goType.Kind() == reflect.String && v.Len() == 0 {
+		return pref.ValueOfBytes(nil) // ensure empty string is []byte(nil)
+	}
+	return pref.ValueOfBytes(v.Convert(bytesType).Bytes())
+}
+func (c *bytesConverter) GoValueOf(v pref.Value) reflect.Value {
+	return reflect.ValueOf(v.Bytes()).Convert(c.goType)
+}
+func (c *bytesConverter) IsValidPB(v pref.Value) bool {
+	_, ok := v.Interface().([]byte)
+	return ok
+}
+func (c *bytesConverter) IsValidGo(v reflect.Value) bool {
+	return v.IsValid() && v.Type() == c.goType
+}
+func (c *bytesConverter) New() pref.Value  { return c.def }
+func (c *bytesConverter) Zero() pref.Value { return c.def }
+
+type enumConverter struct {
+	goType reflect.Type
+	def    pref.Value
+}
+
+func newEnumConverter(goType reflect.Type, fd pref.FieldDescriptor) Converter {
+	var def pref.Value
+	if fd.Cardinality() == pref.Repeated {
+		def = pref.ValueOfEnum(fd.Enum().Values().Get(0).Number())
+	} else {
+		def = fd.Default()
+	}
+	return &enumConverter{goType, def}
+}
+
+func (c *enumConverter) PBValueOf(v reflect.Value) pref.Value {
+	if v.Type() != c.goType {
+		panic(fmt.Sprintf("invalid type: got %v, want %v", v.Type(), c.goType))
+	}
+	return pref.ValueOfEnum(pref.EnumNumber(v.Int()))
+}
+
+func (c *enumConverter) GoValueOf(v pref.Value) reflect.Value {
+	return reflect.ValueOf(v.Enum()).Convert(c.goType)
+}
+
+func (c *enumConverter) IsValidPB(v pref.Value) bool {
+	_, ok := v.Interface().(pref.EnumNumber)
+	return ok
+}
+
+func (c *enumConverter) IsValidGo(v reflect.Value) bool {
+	return v.IsValid() && v.Type() == c.goType
+}
+
+func (c *enumConverter) New() pref.Value {
+	return c.def
+}
+
+func (c *enumConverter) Zero() pref.Value {
+	return c.def
+}
+
+type messageConverter struct {
+	goType reflect.Type
+}
+
+func newMessageConverter(goType reflect.Type) Converter {
+	return &messageConverter{goType}
+}
+
+func (c *messageConverter) PBValueOf(v reflect.Value) pref.Value {
+	if v.Type() != c.goType {
+		panic(fmt.Sprintf("invalid type: got %v, want %v", v.Type(), c.goType))
+	}
+	if c.isNonPointer() {
+		if v.CanAddr() {
+			v = v.Addr() // T => *T
+		} else {
+			v = reflect.Zero(reflect.PtrTo(v.Type()))
+		}
+	}
+	if m, ok := v.Interface().(pref.ProtoMessage); ok {
+		return pref.ValueOfMessage(m.ProtoReflect())
+	}
+	return pref.ValueOfMessage(legacyWrapMessage(v))
+}
+
+func (c *messageConverter) GoValueOf(v pref.Value) reflect.Value {
+	m := v.Message()
+	var rv reflect.Value
+	if u, ok := m.(unwrapper); ok {
+		rv = reflect.ValueOf(u.protoUnwrap())
+	} else {
+		rv = reflect.ValueOf(m.Interface())
+	}
+	if c.isNonPointer() {
+		if rv.Type() != reflect.PtrTo(c.goType) {
+			panic(fmt.Sprintf("invalid type: got %v, want %v", rv.Type(), reflect.PtrTo(c.goType)))
+		}
+		if !rv.IsNil() {
+			rv = rv.Elem() // *T => T
+		} else {
+			rv = reflect.Zero(rv.Type().Elem())
+		}
+	}
+	if rv.Type() != c.goType {
+		panic(fmt.Sprintf("invalid type: got %v, want %v", rv.Type(), c.goType))
+	}
+	return rv
+}
+
+func (c *messageConverter) IsValidPB(v pref.Value) bool {
+	m := v.Message()
+	var rv reflect.Value
+	if u, ok := m.(unwrapper); ok {
+		rv = reflect.ValueOf(u.protoUnwrap())
+	} else {
+		rv = reflect.ValueOf(m.Interface())
+	}
+	if c.isNonPointer() {
+		return rv.Type() == reflect.PtrTo(c.goType)
+	}
+	return rv.Type() == c.goType
+}
+
+func (c *messageConverter) IsValidGo(v reflect.Value) bool {
+	return v.IsValid() && v.Type() == c.goType
+}
+
+func (c *messageConverter) New() pref.Value {
+	if c.isNonPointer() {
+		return c.PBValueOf(reflect.New(c.goType).Elem())
+	}
+	return c.PBValueOf(reflect.New(c.goType.Elem()))
+}
+
+func (c *messageConverter) Zero() pref.Value {
+	return c.PBValueOf(reflect.Zero(c.goType))
+}
+
+// isNonPointer reports whether the type is a non-pointer type.
+// This never occurs for generated message types.
+func (c *messageConverter) isNonPointer() bool {
+	return c.goType.Kind() != reflect.Ptr
+}