allows param links in Sphinx function/method descriptions to be linkable

 Sphinx extension which allows :param: directives within Python documentation
 to be linkable.
 .
 Features:
 .
  * :param: directives within Sphinx function/method descriptions will be given a
  paragraph link so that they can be linked to externally.
  * a new text role :paramref: is added, which works like :meth:, :func:, etc.