rename variable, it is maximum value not number of possibilities
set proper image dimensions for palette

It is not used anywhere, but still...
this it is bits
Clean up description.
Actually, the low level API is not exported so remove the comment.
Add an updated overview about provided functions.
remove space before colon
the palettes are three channel RGB, rename accordingly
Merge pull request #63 from iger/cleanup

Some cleanup in Png.hs