Fix for issue #22 for get, post, delete, put, and patch

This enables the examples at in the docs which contain extra params and headers, such as 

    from firebase import firebase
    firebase = firebase.FirebaseApplication('https://your_storage.firebaseio.com', None)
    result = firebase.get('/users/2', None, {'print': 'pretty'}, {'X_FANCY_HEADER': 'VERY FANCY'})
    print result
    {'2': 'Jane Doe'}

to work properly. In the current Master version of python-firebase, the following error is triggered:

    TypeError: get() got multiple values for keyword argument 'connection'