Added document for use of salt-cloud with HP Cloud 1.1

Hi there! I have finally found a way to get salt-cloud to work with HP Cloud 1.1 (OpenStack Grizzly-based). The docs for salt-cloud (salt-cloud.readthedocs.org) is way out of date and even the current docs that are now part of salt itself are lacking some documentation for features that I was only able to find in the source.