improved, but still weird/wrong camera.

based on [tut][], but somehow still wrong. the interesting stuff is in
[shooter.js][], in the functions `rotateView` and `moveView`.

[tut]: http://www.html5rocks.com/en/tutorials/pointerlock/intro
[shooter.js]: http://www.html5rocks.com/en/tutorials/pointerlock/intro/shooter.js