[TIMOB-23147] Tests run on Travis should include apidoc validation script

We've had a couple of situations lately with broken docs because of errors in the YAML files. We have an apidoc validation script: https://github.com/appcelerator/titanium_mobile/blob/master/apidoc/validate.js This should be added to the tests run by Travis: https://github.com/appcelerator/titanium_mobile/blob/master/support/ti_mocha_script/test.js This would make Travis fail on PRs with buggy YAML files and save us headaches. /cc [~bimmel]