added language support

from: http://stackoverflow.com/questions/10538791/how-to-set-the-language-in-speech-recognition-on-android

Needs to be tested (sorry) but it should work like this:
```javascript
voiceRecognitionProxy.voiceRecognition({
   "android.speech.extra.PROMPT": "please say something",
   "android.speech.extra.LANGUAGE_MODEL": "free_form",
   "android.speech.extra.LANGUAGE_PREFERENCE": "en-US",
   "callback": callback_func
});
```