fixes #211
replace the gif optimization with a working version
minor addition
fix gif test, fix gif optimization for palette length < 3
a break
remove a float/int problem
Update test_file_gif.py

remove warning
fix Python 2 compatibility
Merge branch 'master' of https://github.com/d-schmidt/Pillow
limit custom palette size
adjust the transparency index after successful optimize
skip transparency block if transparent color is not used after optimize
Merge pull request #228 from d-schmidt/master

working gif optimization