Do not require to implement method map_name_to_column

[AmShaegar13]

Requiring the model to implement a specific method feels wrong and not rails-like. Better configure aliases through a method call in the model like associations are. E.g.

class User < ActiveRecord::Base
  api_aliases team: 'team.identifier', birthday: :dob
end

This is a breaking change as it requires the models to be changed.

[AmShaegar13]

Adjust README and add CHANGELOG entry.