[Travis] Release the jar when we apply a tag.
[Travis] Release the jar when we apply a tag.

The plugin's jar file can be stored in github releases
(https://github.com/criteo/automerge-plugin/releases) after a
travis build. Let's do that each time we apply a tag to the
github account.

criteo/automerge-plugin,criteo/automerge-plugin,criteo/automerge-plugin