Input

I made some changes. Mostly I added a setup.py file for easy installation: you can install narrative module to your python path by typeing $ sudo python setup.py build install
Also I moved the declaration of the namedtuples outside the NarrativeBank body, so that the class can be pickled.
Finally, I changed the input to be a list of file names. This is more general than supplying a directory and allows other users (namely me :) ) more control when adding files to the narrative bank -- for instance I wanted to be able to add files deeper in the directory.