added README.rst for use on PyPi

With help form `pandoc`:
http://johnmacfarlane.net/pandoc/

    pandoc -f markdown -t rst -o README.rst README.md

Also using the `read()` function in `setup.py`
to populate `long_description` with the README.rst
added missing import to setup.py
Merge pull request #15 from cloudant-labs/readme-for-pypi

switching to reStructuredText for PyPi