Test against Rails 3.2, 4.0, 4.1

Remove gemfiles from version control to match same testing style as
Clearance and Suspenders.
Ignore gemfiles, don't ignore Gemfile.lock in git
Test against Ruby 2.1.2
Add bin/setup, improve contributing guidelines

Move manual Appraisal tasks into bin/setup.
Move dev dependencies out of gemspec, into Gemfile

Gain more control over private API.