Fix urls in README.rst
Fix urls in README.rst

1. bug tracking has been moved to storyboard
2. syntax issues
3. remove PyPI downloads since it is no longer maintained
https://packaging.python.org/guides/analyzing-pypi-package-downloads/

Change-Id: Ic57c7032af0296d666841021c19e6e56f0b3e89a

openstack/python-openstackclient,dtroyer/python-openstackclient,dtroyer/python-openstackclient,openstack/python-openstackclient