update vendor

vendor/github.com/go-log/log/LICENSE

+Copyright (c) 2017 Go Log
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

vendor/github.com/go-log/log/README.md

+# Log [![GoDoc](https://godoc.org/github.com/go-log/log?status.svg)](https://godoc.org/github.com/go-log/log)
+
+Log is a logging interface for Go. That's it. Pass around the interface.
+
+## Rationale
+
+Users want to standardise logging. Sometimes libraries log. We leave the underlying logging implementation to the user 
+while allowing libraries to log by simply expecting something that satisfies the Logger interface. This leaves 
+the user free to pre-configure structure, output, etc.
+
+## Interface
+
+The interface is minimalistic on purpose
+
+```go
+type Logger interface {
+    Log(v ...interface{})
+    Logf(format string, v ...interface{})
+}
+```
+
+## Example
+
+Here's a logger that uses logrus and logs with predefined fields.
+
+```go
+import (
+	"github.com/go-log/log"
+	"github.com/sirupsen/logrus"
+)
+
+type logrusLogger struct {
+	*logrus.Entry
+}
+
+func (l *logrusLogger) Log(v ...interface{}) {
+	l.Entry.Print(v...)
+}
+
+func (l *logrusLogger) Logf(format string, v ...interface{}) {
+	l.Entry.Printf(format, v...)
+}
+
+func WithFields(f logrus.Fields) log.Logger {
+	return &logrusLogger{logrus.WithFields(f)}	
+}
+```
+
+The `WithFields` func returns a struct that satisfies the Logger interface.
+
+Pre-configure a logger using WithFields and pass it as an option to a library.
+
+```go
+import "github.com/lib/foo"
+
+l := mylogger.WithFields(logrus.Fields{
+	"library": "github.com/lib/foo",
+})
+
+f := foo.New(
+	foo.WithLogger(l),
+)
+```

vendor/github.com/go-log/log/log.go

+// Package log provides a log interface
+package log
+
+// Logger is a generic logging interface
+type Logger interface {
+	Log(v ...interface{})
+	Logf(format string, v ...interface{})
+}
+
+var (
+	// The global default logger
+	DefaultLogger Logger = &noOpLogger{}
+)
+
+// noOpLogger is used as a placeholder for the default logger
+type noOpLogger struct{}
+
+func (n *noOpLogger) Log(v ...interface{}) {}
+
+func (n *noOpLogger) Logf(format string, v ...interface{}) {}
+
+// Log logs using the default logger
+func Log(v ...interface{}) {
+	DefaultLogger.Log(v...)
+}
+
+// Logf logs formatted using the default logger
+func Logf(format string, v ...interface{}) {
+	DefaultLogger.Logf(format, v...)
+}

vendor/vendor.json

@@ -33,6 +33,12 @@
 			"revision": "f90acb425616767b84789d10e50a6fb652cd1e9a",
 			"revisionTime": "2017-02-05T06:05:58Z"
 		},
+		{
+			"checksumSHA1": "fBx0fqiyrl26gkGo14J9pJ8zB2Y=",
+			"path": "github.com/go-log/log",
+			"revision": "37e2e1f19306361e1fc152a1839f1236149cb4e4",
+			"revisionTime": "2017-05-15T17:08:25Z"
+		},
 		{
 			"checksumSHA1": "URsJa4y/sUUw/STmbeYx9EKqaYE=",
 			"path": "github.com/golang/glog",