performance optimization

The #uri_path method, which is added to all resourceful models called
unnessarily  #pluralize and #underscore on the model's class name on
every call. The result can be stored at boot time.
inline api documentation (experimental)

The field configuarations (readables/writables) allow to add comments
for the fields. As for now the comments can only be retrieved directly
from Model.toast_config(media_type).apidoc.

Experimental, incomplete and undocumented feature.
fixes for test suite

include Ruby 2.0.0 as testing option
bugfixes