Create branches according to elasticsearch versions
We create branches:

* es-0.90 for elasticsearch 0.90
* es-1.0 for elasticsearch 1.0
* es-1.1 for elasticsearch 1.1
* master for elasticsearch master

We also check that before releasing we don't have a dependency to an elasticsearch SNAPSHOT version.

Add links to each version in documentation

(cherry picked from commit 35f5901)