Added several changes to work with the latest Rexster.

Currently getting the following error during Titan startup:

Exception in thread "main" java.lang.NoSuchMethodError: com.tinkerpop.rexster.server.RexsterApplication.getMetricRegistry()Lcom/yammer/metrics/MetricRegistry;
	at com.thinkaurelius.titan.tinkerpop.rexster.RexsterTitanServer.start(RexsterTitanServer.java:65)
	at com.thinkaurelius.titan.tinkerpop.rexster.RexsterTitanServer.startDaemon(RexsterTitanServer.java:88)
	at com.thinkaurelius.titan.tinkerpop.rexster.RexsterTitanServer.main(RexsterTitanServer.java:126)