Clearer explanation for porting https://github.com/magical/pokemon-sprites-rby to python 2.7.
gfx: Transpose blocks of images instead of only the first block.

This allows transposed images to be grouped together (e.g. animations).
gfx: Decompress graphics that can be converted to png.

Before, converting a .2bpp.lz file required calling decompress and convert_to_png
on the compressed and decompressed files respectively.

gfx.py unlz {}.lz
gfx.py png {}

Putting a .lz file into convert_to_png would raise an exception.

Instead, passing compressed graphics into convert_to_png will decompress them first.
This skips the (now optional) manual decompress step.