Add specs for ActiveRecord implementation.

Need to manually specify the gem file to run specs, e.g.
`BUNDLE_GEMFILE=gemfiles/active_record4.gemfile bundle exec rspec`.

Current spec status:
  standalone: 68 examples, 0 failures in 0.1352 seconds.
  ActiveRecord 4: 124 examples, 0 failures in 0.14502 seconds.
Add multi-Gemfile support to Travis CI config.
Fix error expectations, missing params abstraction.

Current spec status:
  standalone: 68 examples, 0 failures in 0.10521 seconds.
  ActiveRecord 4: 124 examples, 0 failures in 0.14419 seconds.
Fix .travis.yml gemfile specification.
Add MockController behavior specs.

Current spec status:
  standalone: 72 examples, 0 failures in 0.11217 seconds.
  ActiveRecord 4: 132 examples, 0 failures in 0.18266 seconds.
Merge pull request #2 from sleepingkingstudios/sqlite

Add specs for ActiveRecord::Base model object collections.