Added logging

vendor/github.com/op/go-logging/README.md

@@ -0,0 +1,89 @@
+## Golang logging library
+
+[![godoc](http://img.shields.io/badge/godoc-reference-blue.svg?style=flat)](https://godoc.org/github.com/op/go-logging) [![build](https://img.shields.io/travis/op/go-logging.svg?style=flat)](https://travis-ci.org/op/go-logging)
+
+Package logging implements a logging infrastructure for Go. Its output format
+is customizable and supports different logging backends like syslog, file and
+memory. Multiple backends can be utilized with different log levels per backend
+and logger.
+
+## Example
+
+Let's have a look at an [example](examples/example.go) which demonstrates most
+of the features found in this library.
+
+[![Example Output](examples/example.png)](examples/example.go)
+
+```go
+package main
+
+import (
+	"os"
+
+	"github.com/op/go-logging"
+)
+
+var log = logging.MustGetLogger("example")
+
+// Example format string. Everything except the message has a custom color
+// which is dependent on the log level. Many fields have a custom output
+// formatting too, eg. the time returns the hour down to the milli second.
+var format = logging.MustStringFormatter(
+	`%{color}%{time:15:04:05.000} %{shortfunc} ▶ %{level:.4s} %{id:03x}%{color:reset} %{message}`,
+)
+
+// Password is just an example type implementing the Redactor interface. Any
+// time this is logged, the Redacted() function will be called.
+type Password string
+
+func (p Password) Redacted() interface{} {
+	return logging.Redact(string(p))
+}
+
+func main() {
+	// For demo purposes, create two backend for os.Stderr.
+	backend1 := logging.NewLogBackend(os.Stderr, "", 0)
+	backend2 := logging.NewLogBackend(os.Stderr, "", 0)
+
+	// For messages written to backend2 we want to add some additional
+	// information to the output, including the used log level and the name of
+	// the function.
+	backend2Formatter := logging.NewBackendFormatter(backend2, format)
+
+	// Only errors and more severe messages should be sent to backend1
+	backend1Leveled := logging.AddModuleLevel(backend1)
+	backend1Leveled.SetLevel(logging.ERROR, "")
+
+	// Set the backends to be used.
+	logging.SetBackend(backend1Leveled, backend2Formatter)
+
+	log.Debugf("debug %s", Password("secret"))
+	log.Info("info")
+	log.Notice("notice")
+	log.Warning("warning")
+	log.Error("err")
+	log.Critical("crit")
+}
+```
+
+## Installing
+
+### Using *go get*
+
+    $ go get github.com/op/go-logging
+
+After this command *go-logging* is ready to use. Its source will be in:
+
+    $GOPATH/src/pkg/github.com/op/go-logging
+
+You can use `go get -u` to update the package.
+
+## Documentation
+
+For docs, see http://godoc.org/github.com/op/go-logging or run:
+
+    $ godoc github.com/op/go-logging
+
+## Additional resources
+
+* [wslog](https://godoc.org/github.com/cryptix/go/logging/wslog) -- exposes log messages through a WebSocket.