Removed dependency from Twee on wxWidgets

Twee is a command line tool, so it shouldn't depend on a GUI toolkit.
However, the "tweelexer" module contained both GUI functionality and
essential non-GUI definitions. Solved this by splitting off the regex
definitions into the new module "tweeregex" and make Twee import that
instead.
Merge pull request #127 from mthuurne/twee_no_wx

TweeRegex module