Add a DefaultChunkerMaker which would accept a dict for partial equality on key

[PonteIneptique]

See #2

The idea is not to force every one to go through regexp. Instead of doing that, we offer a chunker maker in the following form

def RegExDefaultChunkerMaker(config):
   """
   :param config: Dictionary with keys such as the original
   :type config: dict
   """
   def callback(text, getValidReffCallback):
       # do regexp matching on key
       if match(text.urn, config.keys()):
           return specificfunction
       return config["default"](text, getValidReffCallback)
   return callback