future proofing

INFO msg in demux now looks like:

Oct 24 15:44:41 INFO demux.consumer_stream consumer_stream.py: Received activity on input stream ActivityStreamConsumer, Verb: 28, Published: 2014-10-24T22:44:41.684489Z (Partition: 0, Offset: 1365, HighWaterMark: 1366)