replace blocks with faces
minor cleanups
move shaders out of GLBuffers
clean up glw warnings
GLBuffer -> GLByteArray, GLSliceBuffer -> GLArray
Separate OpenGL VBOs from VAOs
Make IdAllocators more generic
use IdAllocator for texture units, remove load_terrain_textures()
simplify make_terrain slightly
change Texture.id to Texture.gl_id
stop GLByteBuffer from checking pointer alignment
tiny error message change
add an OpenGL BufferTexture struct
use buffer textures to provide shader data; lighting works again
make terrain gen blocks half as large
calculate normals via cross product
perlin noise terrain gen
README update