Small style changes and adding tests

PEP 8 generally suggests 4 spaces per indentation level and not mixing tabs and spaces. The original version of the file had mixed tabs and spaces and was indented at 8 spaces per level.

Besides fixing that and the addition of tests, I also added a simple API function for people just wishing to parse text without having to instantiate and run a PyFuck instance.

Let me know how you like the request. I'll be happy to fix anything up to your liking.