Fix create_column_family() docstring (issue #35)
Fix create_column_family() docstring (issue #35)

 * Take out parameter types where multiple types are possible;
   Sphinx doesn't like more than one type
 * Use the correct parameter names for key_cache_save_period_in_seconds
   and row_cache_save_period_in_seconds in the docstring.

pycassa/pycassa,pycassa/pycassa