Fixing behavior for ruby 2.1.1
Adding multi rails support
Removing Sprockets dependency
Updating engine to fix matrix specs
Replacing derived ActiveModel linter

Instead of using the indirection of the ActiveModel::Lint::Tests, I'm
explicitly declaring the tests.
Replacing derived ActiveModel linter

Instead of using the indirection of the ActiveModel::Lint::Tests, I'm
explicitly declaring the tests.
Removing Rails 3 support
Merge branch 'adding-multi-rails-support'

* adding-multi-rails-support:
  Removing Rails 3 support
  Replacing derived ActiveModel linter
  Updating engine to fix matrix specs
  Removing Sprockets dependency
  Adding multi rails support