Remove .ruby-version

Weird ruby-version causing problems - better to leave it out.
Change Rspec #color_enabled to #color

color_enabled is an alias for color and was removed in later versions
Add Rakefile

When entering a new project, I generally expect "bundle exec rake" to run the tests and "Just Work".
Merge pull request #6 from nateberkopec/test-niceties

Fix some weird stuff in development/test