Add label option for DailyRotateFile transport

This option is missing from this transport but available in the others

lib/winston/transports/daily-rotate-file.js

@@ -69,6 +69,7 @@ var DailyRotateFile = exports.DailyRotateFile = function (options) {
   this.colorize    = options.colorize    || false;
   this.maxsize     = options.maxsize     || null;
   this.maxFiles    = options.maxFiles    || null;
+  this.label       = options.label       || null;
   this.prettyPrint = options.prettyPrint || false;
   this.timestamp   = options.timestamp != null ? options.timestamp : true;
   this.datePattern = options.datePattern != null ? options.datePattern : '.yyyy-MM-dd';
@@ -154,6 +155,7 @@ DailyRotateFile.prototype.log = function (level, msg, meta, callback) {
     colorize:    this.colorize,
     prettyPrint: this.prettyPrint,
     timestamp:   this.timestamp,
+    label:       this.label,
     stringify:   this.stringify
   }) + '\n';