Updated rackspace-novaclient link in setting up Supernova

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post on setting up supernova so that the rackspace-novaclient will link to the most recent version as a opposed to the outdated version.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