gitignore: added build/ and *patch
voxel: changed shebang to work with virtualenv
voxel: restructured source code
core: only bind VBO if there are any voxels to render
app: added Config class
voxel: removed data loading from App

This is a move towards having the App as a base class that is agnostic to the
particular format used to store data.
app: added a simple keymap
app: added key binds to the configuration
app: added resolution attribute
app: added add_point function
voxel: added VoxelApp subclass

Added the VoxelApp so illustrate the intended way for data to loaded.
Merge branch 'staging'