Tell Travis to notify Gitter with build statuses

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Merge pull request #2270 from opf/feature/travisci-notify-gitter
Merge branch 'release/4.0' into dev

Signed-off-by: Alex Coles <alex@alexbcoles.com>

Conflicts:
	.travis.yml