pylearn2/datasets now pep8-clean

Autopep8'ed, inspected, manually fixed.
l=[0,1,2,3]
old i in [1,2]
old acces: l[:1+1], l[:2+1]
new i in [2]
new access: [:2]

It isn't equivalent. The new code won't create the last directory. So revert this change. Don't forget, when we slice start:stop, we exclude the stop. If we where including the stop, it would be a good change.