How to trigger RMG tests when both RMG and database are non master branches

There's lots of cases where a new feature requires both changes in RMG-Py and RMG-database. We've already got a way to run travis unittest by modifying .travis.yml of RMG-Py or RMG-database, but still need similar guide for triggering RMG-tests for those cases.

The modification is simple. One should go to deploy.sh of RMG-Py and apply changes similar as follows:

RMGTESTSBRANCH=rmgpydb-$DEPLOY_BRANCH
...
DB_DEPLOY_BRANCH="your_rmgdb_branch_name"
git commit --allow-empty -m rmgpydb-$REV-${DB_DEPLOY_BRANCH}

which creates a branch in RMG-tests repo with starting keyword of rmgpydb, notifying travis to grab another piece of RMG-database information from the last commit message DB_DEPLOY_BRANCH