Added new travis test runs that use yajl, multi_json and uuidtools

We have a few extra code paths that will only be activated if we use
one of these gems. Adding them to the build matrix should cover those
cases with all the tests in the regular test suite.
Made sure gemfiles point to the gemspec in the root directory

Previously travis was failing because it was looking for a gemspec in
the gemfiles directory
Made sure strings in .travis.yml are quoted the same way