doc: add documentation basic with sphinx
feed: split OpenMensaCanteen into strict and lazy classes
feed: convert to spaces
tests: convert to spaces (PEP8)
feed: add tests for canteen objects + fix bug in price output
doc: extend feed documentation and change html theme
README: Rewrite README - references sphinx doc and add tldr
feed: fixes LazyCanteen inheritance (uses New-Style-Classes in Python2)