Modified the post on setting up supernova so that the rackspace-novaclient will link to the most recent version as a opposed to the outdated version.

Before: http://pypi.python.org/pypi/rackspace-novaclient/1.1
After: http://pypi.python.org/pypi/rackspace-novaclient/
Merge pull request #65 from mralexjuarez/master

Updated rackspace-novaclient link in setting up Supernova