[#30] Set up test / code linting tools + add Travis continuous integration

[krissy]

Addresses issue #30 + some extra bits

What this does

Some general cleanup and setup for testing, code linting and continuous integration going forward.

Tasks

• [x] Clean out unused files
• [x] Add linting tool (rubocop) and clean-up code based on initial run
• [x] Add testing tools/configuration
• [x] Add factories for Drawing and User models
• [x] Add some initial tests for Drawing models/controllers to kickstart coverage (others can use this as a basis to add more tests)
• [x] Add some validations to the Drawings model
• [x] Add CI via travis (builds here: https://travis-ci.org/empowerhack/DrawMyLife-Service)
• [x] Add sloth

[steverabino]

Not much else I can add! If it passes, I'm happy! 🎉

[steverabino]

:+1: