fix contextual voice menu

fix the contextual voice menu.
http://stackoverflow.com/questions/25763731/hello-world-in-google-glass/25765062?noredirect=1#comment40915718_25765062

A couple things:
- not sure why you call finish() so I comment it out.
- <trigger keyword="@string/glass_voice_trigger" /> if you don't care about the network, just leave out the constraint.
- For now, I start the HelloActivity when a user trigger the antifreeze menu just for giving example.
```
case R.id.glass_submenu_antifreeze_item:
                    startActivity(new Intent(MenuActivity.this, HelloActivity.class));
                    System.out.println("Menu item called: anti-freeze.\n");
                    return true;
```
Hope this helps!