Create branch for es-x.x versions

(cherry picked from commit aaae6f6)
Update to elasticsearch 1.2.0

Closes #25.

(cherry picked from commit 9f94556)
Race condition: exception while closing the river

Closes #28.

(cherry picked from commit d68f3e7)
Update to elasticsearch 1.3.0

Closes #26.
(cherry picked from commit 06f73b2)
Update to elasticsearch 1.4.0

Closes #27.
(cherry picked from commit b1f34ca)
Update for es 2.0.0