Fix getting started with minitest framework feature

[nando]

Summary

I followed the Getting Started with Aruba feature in order to use Aruba in my Minitest build and discovered a typo in the Aruba's setup method name, and also the reason why it wasn't detected by Aruba's current build: the test method name in the feature didn't start with "test_", so it never runs.

Details

• I add "test_" to the test method name
• I update the Aruba's setup call (from aruba_setup to setup_aruba)
• I use assert_equal instead of #must_equal in the test implementation to avoid Minitest error.

[mvz]

Thanks @nando! That looks good. Can you please rebase this on current master and combine commits to get rid of the 'oops' commits?

[mvz]

@nando do you need any help rebasing this?

[mvz]

Superseded by #921.