Add rubocop into Travis-CI

[colby-swandale]

Note: This PR depends on #282 being merged first.

This PR adds a step in Travis to run rubocop. This would be very beneficial to the project because it makes sure that any new changes to rake conform to the existing style guide.

[coveralls]

Coverage decreased (-0.2%) to 97.574% when pulling 606e613 on colby-swandale:colby/add-rubocop-into-ci into f0c7528 on ruby:master.

[colby-swandale]

This has been rebased with master

[yuki24]

I'd personally prefer to add lint checks to git hooks as it catches syntactical mistakes early. Lint checks on CI create a long feedback loop depending on how many jobs are in the queue.

[colby-swandale]

Thanks for the feedback @yuki24. I think both are good practices to have in a project. Having Rubocop in a git hook and having a quick feedback loop is super handy for developers. But also having a final check before any code is merged helps prevent any mistakes from getting into master.

Not everyone likes/uses git hooks, i personally don't use them, and IMO shouldn't be forced onto developers.

[fatkodima]

Lint checks on CI create a long feedback loop

For this project, rubocop will run under several seconds.

[fatkodima]

I am trying to run rubocop locally and it fails to start. So I'm guessing no one runs it under git hooks also? 😄