fix deprecated bundler source
bring ActiveRecord 4 compatibility
test ActiveRecord 4 on travis-ci
set attr_accessible for ActiveRecord < 4
bump activerecord from beta to rc
fix failing spec with ActiveRecord 4

See: https://github.com/rails/arel/pull/177
check for strong_parameters module instead of ActiveRecord version
Merge pull request #43 from NARKOZ/rails4

Rails 4 support