diff --git a/vendor/google.golang.org/grpc/codes/code_string.go b/vendor/google.golang.org/grpc/codes/code_string.go
new file mode 100644
index 0000000..0b206a5
--- /dev/null
+++ b/vendor/google.golang.org/grpc/codes/code_string.go
@@ -0,0 +1,62 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package codes
+
+import "strconv"
+
+func (c Code) String() string {
+	switch c {
+	case OK:
+		return "OK"
+	case Canceled:
+		return "Canceled"
+	case Unknown:
+		return "Unknown"
+	case InvalidArgument:
+		return "InvalidArgument"
+	case DeadlineExceeded:
+		return "DeadlineExceeded"
+	case NotFound:
+		return "NotFound"
+	case AlreadyExists:
+		return "AlreadyExists"
+	case PermissionDenied:
+		return "PermissionDenied"
+	case ResourceExhausted:
+		return "ResourceExhausted"
+	case FailedPrecondition:
+		return "FailedPrecondition"
+	case Aborted:
+		return "Aborted"
+	case OutOfRange:
+		return "OutOfRange"
+	case Unimplemented:
+		return "Unimplemented"
+	case Internal:
+		return "Internal"
+	case Unavailable:
+		return "Unavailable"
+	case DataLoss:
+		return "DataLoss"
+	case Unauthenticated:
+		return "Unauthenticated"
+	default:
+		return "Code(" + strconv.FormatInt(int64(c), 10) + ")"
+	}
+}
diff --git a/vendor/google.golang.org/grpc/codes/codes.go b/vendor/google.golang.org/grpc/codes/codes.go
new file mode 100644
index 0000000..d9b9d57
--- /dev/null
+++ b/vendor/google.golang.org/grpc/codes/codes.go
@@ -0,0 +1,197 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package codes defines the canonical error codes used by gRPC. It is
+// consistent across various languages.
+package codes // import "google.golang.org/grpc/codes"
+
+import (
+	"fmt"
+	"strconv"
+)
+
+// A Code is an unsigned 32-bit error code as defined in the gRPC spec.
+type Code uint32
+
+const (
+	// OK is returned on success.
+	OK Code = 0
+
+	// Canceled indicates the operation was canceled (typically by the caller).
+	Canceled Code = 1
+
+	// Unknown error. An example of where this error may be returned is
+	// if a Status value received from another address space belongs to
+	// an error-space that is not known in this address space. Also
+	// errors raised by APIs that do not return enough error information
+	// may be converted to this error.
+	Unknown Code = 2
+
+	// InvalidArgument indicates client specified an invalid argument.
+	// Note that this differs from FailedPrecondition. It indicates arguments
+	// that are problematic regardless of the state of the system
+	// (e.g., a malformed file name).
+	InvalidArgument Code = 3
+
+	// DeadlineExceeded means operation expired before completion.
+	// For operations that change the state of the system, this error may be
+	// returned even if the operation has completed successfully. For
+	// example, a successful response from a server could have been delayed
+	// long enough for the deadline to expire.
+	DeadlineExceeded Code = 4
+
+	// NotFound means some requested entity (e.g., file or directory) was
+	// not found.
+	NotFound Code = 5
+
+	// AlreadyExists means an attempt to create an entity failed because one
+	// already exists.
+	AlreadyExists Code = 6
+
+	// PermissionDenied indicates the caller does not have permission to
+	// execute the specified operation. It must not be used for rejections
+	// caused by exhausting some resource (use ResourceExhausted
+	// instead for those errors). It must not be
+	// used if the caller cannot be identified (use Unauthenticated
+	// instead for those errors).
+	PermissionDenied Code = 7
+
+	// ResourceExhausted indicates some resource has been exhausted, perhaps
+	// a per-user quota, or perhaps the entire file system is out of space.
+	ResourceExhausted Code = 8
+
+	// FailedPrecondition indicates operation was rejected because the
+	// system is not in a state required for the operation's execution.
+	// For example, directory to be deleted may be non-empty, an rmdir
+	// operation is applied to a non-directory, etc.
+	//
+	// A litmus test that may help a service implementor in deciding
+	// between FailedPrecondition, Aborted, and Unavailable:
+	//  (a) Use Unavailable if the client can retry just the failing call.
+	//  (b) Use Aborted if the client should retry at a higher-level
+	//      (e.g., restarting a read-modify-write sequence).
+	//  (c) Use FailedPrecondition if the client should not retry until
+	//      the system state has been explicitly fixed. E.g., if an "rmdir"
+	//      fails because the directory is non-empty, FailedPrecondition
+	//      should be returned since the client should not retry unless
+	//      they have first fixed up the directory by deleting files from it.
+	//  (d) Use FailedPrecondition if the client performs conditional
+	//      REST Get/Update/Delete on a resource and the resource on the
+	//      server does not match the condition. E.g., conflicting
+	//      read-modify-write on the same resource.
+	FailedPrecondition Code = 9
+
+	// Aborted indicates the operation was aborted, typically due to a
+	// concurrency issue like sequencer check failures, transaction aborts,
+	// etc.
+	//
+	// See litmus test above for deciding between FailedPrecondition,
+	// Aborted, and Unavailable.
+	Aborted Code = 10
+
+	// OutOfRange means operation was attempted past the valid range.
+	// E.g., seeking or reading past end of file.
+	//
+	// Unlike InvalidArgument, this error indicates a problem that may
+	// be fixed if the system state changes. For example, a 32-bit file
+	// system will generate InvalidArgument if asked to read at an
+	// offset that is not in the range [0,2^32-1], but it will generate
+	// OutOfRange if asked to read from an offset past the current
+	// file size.
+	//
+	// There is a fair bit of overlap between FailedPrecondition and
+	// OutOfRange. We recommend using OutOfRange (the more specific
+	// error) when it applies so that callers who are iterating through
+	// a space can easily look for an OutOfRange error to detect when
+	// they are done.
+	OutOfRange Code = 11
+
+	// Unimplemented indicates operation is not implemented or not
+	// supported/enabled in this service.
+	Unimplemented Code = 12
+
+	// Internal errors. Means some invariants expected by underlying
+	// system has been broken. If you see one of these errors,
+	// something is very broken.
+	Internal Code = 13
+
+	// Unavailable indicates the service is currently unavailable.
+	// This is a most likely a transient condition and may be corrected
+	// by retrying with a backoff.
+	//
+	// See litmus test above for deciding between FailedPrecondition,
+	// Aborted, and Unavailable.
+	Unavailable Code = 14
+
+	// DataLoss indicates unrecoverable data loss or corruption.
+	DataLoss Code = 15
+
+	// Unauthenticated indicates the request does not have valid
+	// authentication credentials for the operation.
+	Unauthenticated Code = 16
+
+	_maxCode = 17
+)
+
+var strToCode = map[string]Code{
+	`"OK"`: OK,
+	`"CANCELLED"`:/* [sic] */ Canceled,
+	`"UNKNOWN"`:             Unknown,
+	`"INVALID_ARGUMENT"`:    InvalidArgument,
+	`"DEADLINE_EXCEEDED"`:   DeadlineExceeded,
+	`"NOT_FOUND"`:           NotFound,
+	`"ALREADY_EXISTS"`:      AlreadyExists,
+	`"PERMISSION_DENIED"`:   PermissionDenied,
+	`"RESOURCE_EXHAUSTED"`:  ResourceExhausted,
+	`"FAILED_PRECONDITION"`: FailedPrecondition,
+	`"ABORTED"`:             Aborted,
+	`"OUT_OF_RANGE"`:        OutOfRange,
+	`"UNIMPLEMENTED"`:       Unimplemented,
+	`"INTERNAL"`:            Internal,
+	`"UNAVAILABLE"`:         Unavailable,
+	`"DATA_LOSS"`:           DataLoss,
+	`"UNAUTHENTICATED"`:     Unauthenticated,
+}
+
+// UnmarshalJSON unmarshals b into the Code.
+func (c *Code) UnmarshalJSON(b []byte) error {
+	// From json.Unmarshaler: By convention, to approximate the behavior of
+	// Unmarshal itself, Unmarshalers implement UnmarshalJSON([]byte("null")) as
+	// a no-op.
+	if string(b) == "null" {
+		return nil
+	}
+	if c == nil {
+		return fmt.Errorf("nil receiver passed to UnmarshalJSON")
+	}
+
+	if ci, err := strconv.ParseUint(string(b), 10, 32); err == nil {
+		if ci >= _maxCode {
+			return fmt.Errorf("invalid code: %q", ci)
+		}
+
+		*c = Code(ci)
+		return nil
+	}
+
+	if jc, ok := strToCode[string(b)]; ok {
+		*c = jc
+		return nil
+	}
+	return fmt.Errorf("invalid code: %q", string(b))
+}