Adding screen orientation sample

The Promise always rejects with a "This page needs to be fullscreen in order to lock orientation." error. (Tested on Chrome 38.0.2125.57 on Android.)

I think that's part of the spec. If you wanted to demonstrate the fullscreen + orientation lock process, I'm sure that would be useful. Alternatively, you could just remove the code that attempt to lock and add some explanatory text about needing to go fullscreen first.