Add support for markdown parsing of docstring.

* Markdown parsing using misaka[1] that supports github
  flavoured syntax.
* use inspect.getdoc to clean up the whitespaces.

[1]: https://github.com/FSX/misaka
[2]: http://bit.ly/1bZvBdY

Signed-off-by: Saurabh Kumar <thes.kumar@gmail.com>