Running tests with setuptools.
Remove requirements.txt file and scripts using it.
Add workaround to remove exception after tests.

Exception example: https://travis-ci.org/iurisilvio/Flask-Images/builds/15532521
Workaround: http://bugs.python.org/issue15881#msg170215
Use Pillow instead of PIL because it is not setuptools compatible.
Merge branch 'tests'
Depend on a Pillow wrapper instead
Merge branch 'pillow'