Add a Gemfile for Rails 4.2
WIP
fix travis build
Do not build Rails 5 with ruby < 2.1
Fix <attribute>_before_type_cast on Rails 4.2
Avoid `serialized_attributes` deprecation notice
Avoid reset_<attribute>! deprecation notice
ActiveRecord 4.2 is more strict with PG arrays now.
Merge pull request #21 from byroot/rails-4-2

Rails 4.2.0-rc1 support