Add travis to main gem repo

[kerrizor]

Nice to have, should only take a few minutes.

[riktimmondal]

I would like to commit can you elaborate how to approach it

[kerrizor]

@riktimmondal Sure! There should be a number of how-tos online, here's one to start with: http://pete-hamilton.co.uk/2012/11/17/adding-travis-ci-to-a-ruby-project/

I would expect it is a matter of adding a .travis.yml and once that's done, someone with the right permissions to this repo (me? Chad?) need to do a little twiddling. If you get the YML stuff in place and make sure the rest of the checklist of what we need in the repo is set, I'll merge and do the final set up piece.