infer spec type (example group) from folder location for all custom types

* Added custom example groups for all types so you can do `rspec --tag type:presenter` without having to add a type to each presenter (as long as it's in `spec/presenters`). For our app they should always be in the appropriate folder.
* Removed `RSpec.` prefix from `describe` - I don't see any reason why we need to protect the global namespace completely given we are in the context of a spec. If not agreed we should disable it completely but let's choose one or the other