Fixed issue with naming ES indexes by date.
Fixed issue with naming ES indexes by date.

Should have used UTC dates.

satanovskyj/statsd-elasticsearch-backend,actmd/statsd-elasticsearch-backend,adaptiv-io/statsd-elasticsearch-backend,markkimsal/statsd-elasticsearch-backend,adaptiv-io/statsd-elasticsearch-backend,satanovskyj/statsd-elasticsearch-backend,markkimsal/statsd-elasticsearch-backend,actmd/statsd-elasticsearch-backend