Update dotfiles

* I removed unsupported options from `.jshintrc`. [`trailing` and `smarttabs` options are no longer supported](https://github.com/jshint/jshint/releases/tag/2.5.0).
* I added `sudo: false` to `.travis.yml` [to use container-based infrastructure](http://docs.travis-ci.com/user/workers/container-based-infrastructure/). It's really faster than ever.