diff --git a/vendor/github.com/rs/zerolog/log.go b/vendor/github.com/rs/zerolog/log.go
new file mode 100644
index 0000000..8eb45a8
--- /dev/null
+++ b/vendor/github.com/rs/zerolog/log.go
@@ -0,0 +1,400 @@
+// Package zerolog provides a lightweight logging library dedicated to JSON logging.
+//
+// A global Logger can be use for simple logging:
+//
+//     import "github.com/rs/zerolog/log"
+//
+//     log.Info().Msg("hello world")
+//     // Output: {"time":1494567715,"level":"info","message":"hello world"}
+//
+// NOTE: To import the global logger, import the "log" subpackage "github.com/rs/zerolog/log".
+//
+// Fields can be added to log messages:
+//
+//     log.Info().Str("foo", "bar").Msg("hello world")
+//     // Output: {"time":1494567715,"level":"info","message":"hello world","foo":"bar"}
+//
+// Create logger instance to manage different outputs:
+//
+//     logger := zerolog.New(os.Stderr).With().Timestamp().Logger()
+//     logger.Info().
+//            Str("foo", "bar").
+//            Msg("hello world")
+//     // Output: {"time":1494567715,"level":"info","message":"hello world","foo":"bar"}
+//
+// Sub-loggers let you chain loggers with additional context:
+//
+//     sublogger := log.With().Str("component": "foo").Logger()
+//     sublogger.Info().Msg("hello world")
+//     // Output: {"time":1494567715,"level":"info","message":"hello world","component":"foo"}
+//
+// Level logging
+//
+//     zerolog.SetGlobalLevel(zerolog.InfoLevel)
+//
+//     log.Debug().Msg("filtered out message")
+//     log.Info().Msg("routed message")
+//
+//     if e := log.Debug(); e.Enabled() {
+//         // Compute log output only if enabled.
+//         value := compute()
+//         e.Str("foo": value).Msg("some debug message")
+//     }
+//     // Output: {"level":"info","time":1494567715,"routed message"}
+//
+// Customize automatic field names:
+//
+//     log.TimestampFieldName = "t"
+//     log.LevelFieldName = "p"
+//     log.MessageFieldName = "m"
+//
+//     log.Info().Msg("hello world")
+//     // Output: {"t":1494567715,"p":"info","m":"hello world"}
+//
+// Log with no level and message:
+//
+//     log.Log().Str("foo","bar").Msg("")
+//     // Output: {"time":1494567715,"foo":"bar"}
+//
+// Add contextual fields to global Logger:
+//
+//     log.Logger = log.With().Str("foo", "bar").Logger()
+//
+// Sample logs:
+//
+//     sampled := log.Sample(&zerolog.BasicSampler{N: 10})
+//     sampled.Info().Msg("will be logged every 10 messages")
+//
+// Log with contextual hooks:
+//
+//     // Create the hook:
+//     type SeverityHook struct{}
+//
+//     func (h SeverityHook) Run(e *zerolog.Event, level zerolog.Level, msg string) {
+//          if level != zerolog.NoLevel {
+//              e.Str("severity", level.String())
+//          }
+//     }
+//
+//     // And use it:
+//     var h SeverityHook
+//     log := zerolog.New(os.Stdout).Hook(h)
+//     log.Warn().Msg("")
+//     // Output: {"level":"warn","severity":"warn"}
+//
+//
+// Caveats
+//
+// There is no fields deduplication out-of-the-box.
+// Using the same key multiple times creates new key in final JSON each time.
+//
+//     logger := zerolog.New(os.Stderr).With().Timestamp().Logger()
+//     logger.Info().
+//            Timestamp().
+//            Msg("dup")
+//     // Output: {"level":"info","time":1494567715,"time":1494567715,"message":"dup"}
+//
+// However, it’s not a big deal though as JSON accepts dup keys,
+// the last one prevails.
+package zerolog
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"strconv"
+)
+
+// Level defines log levels.
+type Level uint8
+
+const (
+	// DebugLevel defines debug log level.
+	DebugLevel Level = iota
+	// InfoLevel defines info log level.
+	InfoLevel
+	// WarnLevel defines warn log level.
+	WarnLevel
+	// ErrorLevel defines error log level.
+	ErrorLevel
+	// FatalLevel defines fatal log level.
+	FatalLevel
+	// PanicLevel defines panic log level.
+	PanicLevel
+	// NoLevel defines an absent log level.
+	NoLevel
+	// Disabled disables the logger.
+	Disabled
+)
+
+func (l Level) String() string {
+	switch l {
+	case DebugLevel:
+		return "debug"
+	case InfoLevel:
+		return "info"
+	case WarnLevel:
+		return "warn"
+	case ErrorLevel:
+		return "error"
+	case FatalLevel:
+		return "fatal"
+	case PanicLevel:
+		return "panic"
+	case NoLevel:
+		return ""
+	}
+	return ""
+}
+
+// ParseLevel converts a level string into a zerolog Level value.
+// returns an error if the input string does not match known values.
+func ParseLevel(levelStr string) (Level, error) {
+	switch levelStr {
+	case DebugLevel.String():
+		return DebugLevel, nil
+	case InfoLevel.String():
+		return InfoLevel, nil
+	case WarnLevel.String():
+		return WarnLevel, nil
+	case ErrorLevel.String():
+		return ErrorLevel, nil
+	case FatalLevel.String():
+		return FatalLevel, nil
+	case PanicLevel.String():
+		return PanicLevel, nil
+	case NoLevel.String():
+		return NoLevel, nil
+	}
+	return NoLevel, fmt.Errorf("Unknown Level String: '%s', defaulting to NoLevel", levelStr)
+}
+
+// A Logger represents an active logging object that generates lines
+// of JSON output to an io.Writer. Each logging operation makes a single
+// call to the Writer's Write method. There is no guaranty on access
+// serialization to the Writer. If your Writer is not thread safe,
+// you may consider a sync wrapper.
+type Logger struct {
+	w       LevelWriter
+	level   Level
+	sampler Sampler
+	context []byte
+	hooks   []Hook
+}
+
+// New creates a root logger with given output writer. If the output writer implements
+// the LevelWriter interface, the WriteLevel method will be called instead of the Write
+// one.
+//
+// Each logging operation makes a single call to the Writer's Write method. There is no
+// guaranty on access serialization to the Writer. If your Writer is not thread safe,
+// you may consider using sync wrapper.
+func New(w io.Writer) Logger {
+	if w == nil {
+		w = ioutil.Discard
+	}
+	lw, ok := w.(LevelWriter)
+	if !ok {
+		lw = levelWriterAdapter{w}
+	}
+	return Logger{w: lw}
+}
+
+// Nop returns a disabled logger for which all operation are no-op.
+func Nop() Logger {
+	return New(nil).Level(Disabled)
+}
+
+// Output duplicates the current logger and sets w as its output.
+func (l Logger) Output(w io.Writer) Logger {
+	l2 := New(w)
+	l2.level = l.level
+	l2.sampler = l.sampler
+	if len(l.hooks) > 0 {
+		l2.hooks = append(l2.hooks, l.hooks...)
+	}
+	if l.context != nil {
+		l2.context = make([]byte, len(l.context), cap(l.context))
+		copy(l2.context, l.context)
+	}
+	return l2
+}
+
+// With creates a child logger with the field added to its context.
+func (l Logger) With() Context {
+	context := l.context
+	l.context = make([]byte, 0, 500)
+	if context != nil {
+		l.context = append(l.context, context...)
+	}
+	return Context{l}
+}
+
+// UpdateContext updates the internal logger's context.
+//
+// Use this method with caution. If unsure, prefer the With method.
+func (l *Logger) UpdateContext(update func(c Context) Context) {
+	if l == disabledLogger {
+		return
+	}
+	if cap(l.context) == 0 {
+		l.context = make([]byte, 0, 500)
+	}
+	c := update(Context{*l})
+	l.context = c.l.context
+}
+
+// Level creates a child logger with the minimum accepted level set to level.
+func (l Logger) Level(lvl Level) Logger {
+	l.level = lvl
+	return l
+}
+
+// Sample returns a logger with the s sampler.
+func (l Logger) Sample(s Sampler) Logger {
+	l.sampler = s
+	return l
+}
+
+// Hook returns a logger with the h Hook.
+func (l Logger) Hook(h Hook) Logger {
+	l.hooks = append(l.hooks, h)
+	return l
+}
+
+// Debug starts a new message with debug level.
+//
+// You must call Msg on the returned event in order to send the event.
+func (l *Logger) Debug() *Event {
+	return l.newEvent(DebugLevel, nil)
+}
+
+// Info starts a new message with info level.
+//
+// You must call Msg on the returned event in order to send the event.
+func (l *Logger) Info() *Event {
+	return l.newEvent(InfoLevel, nil)
+}
+
+// Warn starts a new message with warn level.
+//
+// You must call Msg on the returned event in order to send the event.
+func (l *Logger) Warn() *Event {
+	return l.newEvent(WarnLevel, nil)
+}
+
+// Error starts a new message with error level.
+//
+// You must call Msg on the returned event in order to send the event.
+func (l *Logger) Error() *Event {
+	return l.newEvent(ErrorLevel, nil)
+}
+
+// Fatal starts a new message with fatal level. The os.Exit(1) function
+// is called by the Msg method, which terminates the program immediately.
+//
+// You must call Msg on the returned event in order to send the event.
+func (l *Logger) Fatal() *Event {
+	return l.newEvent(FatalLevel, func(msg string) { os.Exit(1) })
+}
+
+// Panic starts a new message with panic level. The panic() function
+// is called by the Msg method, which stops the ordinary flow of a goroutine.
+//
+// You must call Msg on the returned event in order to send the event.
+func (l *Logger) Panic() *Event {
+	return l.newEvent(PanicLevel, func(msg string) { panic(msg) })
+}
+
+// WithLevel starts a new message with level. Unlike Fatal and Panic
+// methods, WithLevel does not terminate the program or stop the ordinary
+// flow of a gourotine when used with their respective levels.
+//
+// You must call Msg on the returned event in order to send the event.
+func (l *Logger) WithLevel(level Level) *Event {
+	switch level {
+	case DebugLevel:
+		return l.Debug()
+	case InfoLevel:
+		return l.Info()
+	case WarnLevel:
+		return l.Warn()
+	case ErrorLevel:
+		return l.Error()
+	case FatalLevel:
+		return l.newEvent(FatalLevel, nil)
+	case PanicLevel:
+		return l.newEvent(PanicLevel, nil)
+	case NoLevel:
+		return l.Log()
+	case Disabled:
+		return nil
+	default:
+		panic("zerolog: WithLevel(): invalid level: " + strconv.Itoa(int(level)))
+	}
+}
+
+// Log starts a new message with no level. Setting GlobalLevel to Disabled
+// will still disable events produced by this method.
+//
+// You must call Msg on the returned event in order to send the event.
+func (l *Logger) Log() *Event {
+	return l.newEvent(NoLevel, nil)
+}
+
+// Print sends a log event using debug level and no extra field.
+// Arguments are handled in the manner of fmt.Print.
+func (l *Logger) Print(v ...interface{}) {
+	if e := l.Debug(); e.Enabled() {
+		e.Msg(fmt.Sprint(v...))
+	}
+}
+
+// Printf sends a log event using debug level and no extra field.
+// Arguments are handled in the manner of fmt.Printf.
+func (l *Logger) Printf(format string, v ...interface{}) {
+	if e := l.Debug(); e.Enabled() {
+		e.Msg(fmt.Sprintf(format, v...))
+	}
+}
+
+// Write implements the io.Writer interface. This is useful to set as a writer
+// for the standard library log.
+func (l Logger) Write(p []byte) (n int, err error) {
+	n = len(p)
+	if n > 0 && p[n-1] == '\n' {
+		// Trim CR added by stdlog.
+		p = p[0 : n-1]
+	}
+	l.Log().Msg(string(p))
+	return
+}
+
+func (l *Logger) newEvent(level Level, done func(string)) *Event {
+	enabled := l.should(level)
+	if !enabled {
+		return nil
+	}
+	e := newEvent(l.w, level)
+	e.done = done
+	e.ch = l.hooks
+	if level != NoLevel {
+		e.Str(LevelFieldName, level.String())
+	}
+	if l.context != nil && len(l.context) > 0 {
+		e.buf = enc.AppendObjectData(e.buf, l.context)
+	}
+	return e
+}
+
+// should returns true if the log event should be logged.
+func (l *Logger) should(lvl Level) bool {
+	if lvl < l.level || lvl < GlobalLevel() {
+		return false
+	}
+	if l.sampler != nil && !samplingDisabled() {
+		return l.sampler.Sample(lvl)
+	}
+	return true
+}