Fix rendered characters have been chipped for some TrueType fonts

ImageFont ignores descender value of TrueType fonts (uses ascender only),
then some fonts which use descender is chipped on rendering.
added dependencies
Merge pull request #145 from wiredfool/travis

added dependencies
basic sanity test for webp
checking results of webp decoding
added write verification test
Fixing deprecation warning on py26
Merge pull request #146 from wiredfool/webp_tests

Webp tests
fixed bug with png-images with transparency palette
fixing save of transparency palette png-images
fix indention
fix indention
Added link to travis-ci page
Merge pull request #151 from Bouke/patch-1

Added link to travis-ci page
fix png decode tRNS pattern
Merge pull request #150 from d-schmidt/master

fixing save of transparency palette png-images
Add tempfile for test output
Merge pull request #153 from manisandro/tempfile

Add tempfile for test output
replaced tabs with space in _imaging.c
Fixes an uninitialized value for an optional parameter.
Effectively, this prevented any remote scanners to be discovered.