'Iterate over the contributors list.
See also: http://developer.github.com/v3/repos/statistics/
.. note:: All statistics methods may return a 202. On those occasions,
you will not receive any objects. You should store your
iterator and check the new ``last_status`` attribute. If it
is a 202 you should wait before re-requesting.
.. versionadded:: 0.7
:param int number: (optional), number of weeks to return. Default -1
will return all of the weeks.
:param str etag: (optional), ETag from a previous request to the same
endpoint
:returns: generator of
:class:`ContributorStats <github3.repos.stats.ContributorStats>`'

def contributor_statistics(self, number=(-1), etag=None):

    url = self._build_url(u'stats', u'contributors', base_url=self._api)
    return self._iter(int(number), url, ContributorStats, etag=etag)
