Fix TestAfkakClientIntegration.test_send_offset_request failure

[twm]

A fix for this failure seen on #37:

[ERROR]
Traceback (most recent call last):
  File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/twisted/internet/defer.py", line 1416, in _inlineCallbacks
    result = result.throwExceptionIntoGenerator(g)
  File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/twisted/python/failure.py", line 512, in throwExceptionIntoGenerator
    return g.throw(self.type, self.value, self.tb)
  File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/afkak/test/int/test_client_integration.py", line 130, in test_send_offset_request
    [resp] = yield self.client.send_offset_request([req])
  File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/twisted/internet/defer.py", line 1418, in _inlineCallbacks
    result = g.send(result)
  File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/afkak/client.py", line 706, in send_offset_request
    returnValue(self._handle_responses(resps, fail_on_error, callback))
  File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/afkak/client.py", line 763, in _handle_responses
    BrokerResponseError.raise_for_errno(resp.error, resp)
  File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/afkak/common.py", line 311, in raise_for_errno
    raise subcls(*args)
afkak.common.NotLeaderForPartitionError: error=6 (NOT_LEADER_FOR_PARTITION) OffsetResponse(topic=u'test_send_offset_request-SMTPHcxJLm', partition=0, error=6, offsets=())
afkak.test.int.test_client_integration.TestAfkakClientIntegration.test_send_offset_request

Simply wait for topic auto-create to complete.

[twm]

(This includes changes from #87 so that should be reviewed and merged first.)

[twm]

Thanks @gobolt!