Add python port

I've ported this to Python (2 and 3)

I chose to set it up as a class rather than a series of methods in order to make it possible to instatiate the Wordfilter with either a custom `list` or a .txt file. 

I had to create a new 'wordfilter' directory because otherwise Python would want to call the package `lib`.

I'd be happy to add code examples to the readme if you'd like.