Update method signature of url_for

Changed in rails 4.2
Defunct
Add dependencies, conventional VERSION constant
Defunct
Update tests: rails 4.2 url_for

> link_to and url_for generate absolute URLs by default in
> templates, it is no longer needed to pass only_path: false.
http://guides.rubyonrails.org/4_2_release_notes.html
Bump version: 2.0.0