Removed whitespace on empty lines in tweelexer.py
Split TweeLexer class

There is a new TweeStyler class, which does what the old TweeLexer
class did: apply styles using wx controls. The TweeLexer class is
now an abstract base class for TweeStyler and VerifyLexer.
Put TweeStyler class in its own module

TweeStyler depends on wxWidgets, while the tweelexer module is used by
the command line "twee" tool as well, which shouldn't depend on any
GUI toolkit.
Merge pull request #142 from mthuurne/twee_no_wx_2

Don't require wx to run twee