start method
Implementation
Future<Stream<String>> start() async {
if (_isRunning) return outStream;
_outStreamController = new StreamController<String>();
_errStreamController = new StreamController<String>();
_process = await Process.start(this.enginePath, []);
_process.stdout.listen(_stdout);
_process.stderr.listen(_stderr);
_isRunning = true;
_outStream = _outStreamController.stream.asBroadcastStream();
_errStream = _errStreamController.stream.asBroadcastStream();
return _outStreamController.stream;
}