Transformers array should be able to include class references

[boardfish]

The transform config option is similar to Active Record Validations in that it looks up transformers based on the symbols you pass it. But if transformers come bundled with Remote Record classes, there's not too much use putting them into some global namespace unless they really need to be.

The aim would be for us to be able to do this:

remote_record do |c|
  c.transform [:snake_case, 'DotParamsTransformer']
end

module DotParamsTransformer
  ...
end