Configure the library for running on TravisCI

Removed dummy apps (we load the schema and models
necessary for testing). Added .travisci.yml with
a variety of environments to test. Added gemfiles
for rails 3, 4, and edge.
Don't allow failures anymore
Switch to RSpec
Isolate expectations
Fix query for Rails 3 where !=
Clean up expectations
Update README regarding testing

[ci skip]
Depend on ActiveRecord, not all of Rails
Merge pull request #18 from shekibobo/travis-setup

Run tests on Travis, on pretty much every environment
Allow certain environments to fail (for now)
Let MySQL fail (for now)
Add test to combine polymorphic associations
Add tests for combined has_many associations
Add specs for combining associations in a couple ways
Add more specs for polymorphic associations
Pass bind values into array correctly