Fix docstring in bitshift/parser/python.py
Minor fix-ups in python parser.
Mod:
    python.py
        - Add self.cache to allow for saving of unassocaited metadata as the
          PyTreeCutter moves down the syntax tree.
        - Update docstrings.
Add first version of the c parser
Add:
    c.py
        - CTreeCutter class is very similar to PyTreeCutter. It utilizes
          self.cache as opposed to PyTreeCutter which doesn't yet.
        - CTreeCutter visit functions simply add start and end lines of
          the node to the cache, and visit_Decl pushes the cache onto
          accum.
        - parse_c performs a task identical to parse_py.  However, many
          c files need to be pre-processed before they are parsed.