Fix missing warn in Loggers

src/common/log/fileLogger.js

@@ -26,6 +26,11 @@ FileLogger.prototype.info = function() {
   fs.appendFileSync(this._filePath, line);
 };
 
+FileLogger.prototype.warn = function() {
+  var line = createLine('WARN', arguments, 0);
+  fs.appendFileSync(this._filePath, line);
+};
+
 FileLogger.prototype.error = function(e) {
   var hasError = e instanceof Error;
   var line = createLine('ERROR', arguments, hasError ? 1 : 0);

src/common/log/noopLogger.js

@@ -1,7 +1,8 @@
 function NoopLogger() {
 }
-NoopLogger.prototype.error = function() {};
 NoopLogger.prototype.debug = function() {};
 NoopLogger.prototype.info = function() {};
+NoopLogger.prototype.warn = function() {};
+NoopLogger.prototype.error = function() {};
 
 module.exports = NoopLogger;