Using local and parallel builds for Travis

[alaxalves]

Make sure these boxes are checked before your pull request is ready to be reviewed and merged. Thanks!

• tests pass -- rake test
• code is in uniquely-named feature branch, and has been rebased on top of latest master (especially if you've been asked to make additional changes)
• pull request are descriptively named
• if possible, multiple commits squashed if they're smaller changes
• reviewed/confirmed/tested by another contributor or maintainer

Please be sure you've reviewed our contribution guidelines at https://publiclab.org/wiki/contributing-to-public-lab-software

Thanks!

[alaxalves]

Split the builds in 3, further we can improve it by splitting the tests, instead of running all tests, split them by 'model, controller, system...'

[SidharthBansal]

LGtM 🎉
However it requires two approval for merging.
@emilyashley has just joined pl. Let's take a review from her.
Jeff is on vacation for Feb.

[emilyashley]

Great, thank you!