[fix] Partial fix for #296. Need to properly detect _isStreams2 cc/…

… @jcruggz.

lib/winston/transports/file.js

@@ -166,6 +166,13 @@ File.prototype.log = function (level, msg, meta, callback) {
 // Write to the stream, ensure execution of a callback on completion.
 //
 File.prototype._write = function(data, callback) {
+  if (this._isStreams2) {
+    this._stream.write(data);
+    return process.nextTick(function () {
+      callback(null, true);
+    });
+  }
+
   // If this is a file write stream, we could use the builtin
   // callback functionality, however, the stream is not guaranteed
   // to be an fs.WriteStream.
@@ -295,11 +302,11 @@ File.prototype.stream = function (options) {
   };
 
   stream.destroy = common.tailFile(tail, function (err, line) {
-    
+
     if(err){
       return stream.emit('error',err);
     }
-    
+
     try {
       stream.emit('data', line);
       line = JSON.parse(line);