Trying to fix .travis.yml for RMG-database project.

This was a direct copy of the RMG-Py project, but it 
needs to be changed if it's for the RMG-database project,
as Travis by default will check out the current project.
Merge branch 'travis'

Travis builds on this RMG-database project now assume the RMG-Py master
is up to date and functioning; they use that, to test the database for
consistency. Currently the tests fail, but that's because there are some
problems with some recent families - the tests themselves seem to be working.

Closes #42