v3.2.0: Rails controller integration

Hi, here's a new version of Alba, v3.2.0. There are two additions in this release.

Now we have a Rails "controller" integration! serialize and render_serialized_json methods are available in Rails controllers, making it easier to use Alba with Rails. It's inspired by Layered Design for Ruby on Rails Applications book mentioning Alba and its usage. Thank you!
Another feature is transform_keys! that enables to change key transformation type after defining a resource/serializer class. It helps when there are so many classes that are almost equivalent. Note that this feature is experimental.

The documentation for the new Rails controller integration is here and the documentation for transform_keys! can be found here.Enjoy!