Renamed 'timestamp' field to '@timestamp'

Makes it easier to use this data in kibana later

Closes #2
Make timestampFieldname configurable

Due to recent changes this change allows to make the timestamp field configurable.

Relates #2
Add sources when building

Closes #3
Support for 1.0

Several changes were necessary to work for 1.0

* Percolation support has changed
* Switched to randomized integration test infrastructure
* Changes in test due to changes in cluster state request
Version bump to 2.0, leaves 1.x to es 0.90 changes
prepare release metrics-elasticsearch-reporter 2.0
prepare for next development iteration