[Libcloud-589] ProfitBricks Compute Driver Support

I have completed support for the ProfitBricks compute driver. This adds support for the core compute driver functions against ProfitBricks. The JIRA ticket can be found here:

https://issues.apache.org/jira/browse/LIBCLOUD-589

Let me know if there are any issues or if it can be accepted or not.

Thanks. 
-matt
@Kami The only issue I have at the moment is with Travis CI. It seems that I'm failing the py3x tests, but all others pass. I'm not sure how to diagnose the issue as it refers to the test_profitbricks module. 

AttributeError: 'module' object has no attribute 'test_profitbricks'
ERROR: InvocationError: '/home/travis/build/apache/libcloud/.tox/py32/bin/python setup.py test'