Add travis-ci settings

Hi!

This change introduce travis-ci settings.

Please turn on the travis hook for this repository in travis-ci.org before merging this change.
http://docs.travis-ci.com/user/getting-started/

If you merge this, you can run test by the command: `npm test`, `./node_modules/.bin/gulp` or `gulp` (all same meanings).

If you have any question, please ask ;)

Thanks,