code: function Transformer( file, res ) {
  			stream.Transform.call( this );
  
  			this.file = file;
  			this.res = res;
  			this.chunks = [];
  		}
docs: Transofrms the code from an incomming stream and outputs the code instrumented by Istanbul
  @param {String} file File name used by Istanbul
  @param {Object} res  HTTP response