Basic first-person camera controls.
* WASD for forward/back and strafe left/right.
* Space/shift for flying up/down, ctrl increases horizontal speed.
* Mouse movement controls yaw (horizontal) and pitch (vertical) angles.
Merge pull request #52 from eddyb/cam-controls

Basic first-person camera controls.
Add NBT decoder.
Implement simple loading of Anvil region files and chunks within.
[WIP] render some minecraft stuff