Allow and ignore arguments set to Cursor.count()

Needed for compatibility with Eve Cursor.count(with_limit_and_skip=None). 
Fixes errors like:
File "/home/adrian/.virtualenvs/server/lib/python3.4/site-packages/eve/methods/get.py", line 128, in get
          count = cursor.count(with_limit_and_skip=False)
      TypeError: count() got an unexpected keyword argument 'with_limit_and_skip'