Flume collector

I've created a flume collector to pull metrics via the json formatted metrics from Flume over HTTP. Very slick way of getting close to real time charts of EPS etc via OpenTSDB.

Tested with Flume 1.4.0 and OpenTSDB 2.0.

Screenshot from StatusWolf with EPS from Flume:

![image](https://cloud.githubusercontent.com/assets/6524147/2811076/99f13002-ce02-11e3-9297-aa799aba9fc0.png)

As the metrics are counters I use the rate function to get the nr of events handled by Flume to events per second.