Update the Mock class to support * imports 

The Mock class in the FAQs currently does not support `from module import *` type imports. As described here http://stackoverflow.com/questions/11877571/how-to-mock-so-that-from-x-import-works the solution is to add `__all__ = []` to the class definition.
Merge pull request #659 from mfitzp/patch-1

Update the Mock class to support * imports