Fix the ceilometer_plugins tox.ini file

DHC-782
* update the url of the ceilometer tarball
* remove old dependencies
* pep8 clean up

Change-Id: I79cf3d1cc071d9284cd4cd471b9801676f5e1680
Merge pull request #64 from rodis/feature/fix-tox-files

Fix the ceilometer_plugins tox.ini file