Http router 0.11
Merge branch 'master' of github.com:padrino/padrino-framework

* 'master' of github.com:padrino/padrino-framework:
  Refactored `button_to` to reuse the `form_tag` helper. Moved it to `form_helpers` to have it on the same namespace (it kind of makes sense for it to be in there) and added some tests to it as well.
  Moved the CSRF authenticity token to be generated on the form_tag helper instead of form_for (the latter uses form_tag at the end anyway...). Added tests too.