read readme in setup.py, for rending on pypi

It would look something like this:
https://testpypi.python.org/pypi/cdap-stream-client/1.0.1

Note: PyPi renders rst text, not md text. So, the readme will not be properly formatted on PyPi if it is not in md format. PanDoc can be used to translate the format, but maybe it would be better to simply replace the current README.md with a README.rst, so we don't have to do this translation often.

Optionally, we can simply link to our github repo for the README, instead of having it both on PyPi and GitHub.