Build on CircleCI

[marcomorain]

• Remove travis config and replace with CircleCI config.
• Ignore test file which is created when running the specs.
• Fix a test that is failing on master, from recent pre-release changes.
• Fix rubocop error

[marcomorain]

The TravisCI build is currently broken, due to some error installing bundler. This was quicker than debugging the issue :trollface:

This requires @KrauseFx to click Follow on https://circleci.com/gh/KrauseFX/xcode-install

[KrauseFx]

Done :)

[marcomorain]

Awesome, thanks <3