Update rails to fix array column default values
Update restpack_serializer gem to edpaget's branch

Rails 4.1.4 changes the value of the `.macro` property of the association object of a
`has_and_belongs_to_many` relation from `:has_many` to
`:has_and_belongs_to_many` I'll be sending a pull request to the master soon.
Merge pull request #127 from edpaget/update-rails

Update rails to fix array column default values