replaced tabs with space in _imaging.c
added tests to cover save of four different png transparencies
Merge branch 'master' of https://github.com/python-imaging/Pillow
Explitly import JpegPresets from the PIL package
Merge pull request #163 from ronaldoussoren/master

Issue 161: import JpegPresets from PIL
Merge pull request #162 from d-schmidt/master

added tests to cover save of four different png transparencies