Fix #141: remove spurious *args / **kwargs from API methods.

That one is a typo in the docs:  the 'force' argument is an explicit parameter for 'connection.delete_bucket', which does nothing with '*args' or '**kwargs':

    Deleting a bucket
    -----------------

    You can delete a bucket using the
    :func:`delete_bucket <gcloud.storage.connection.Connection.delete_bucket>`
    method::

    >>> connection.delete_bucket('my-bucket')

    Remember, the bucket you're deleting needs to be empty,
    otherwise you'll get an error.

    If you have a full bucket, you can delete it this way::

    >>> bucket = connection.get_bucket('my-bucket', force=True)

The last line should obviously be:

    >>> bucket = connection.delete_bucket('my-bucket', force=True)