Update Padrino to 0.11.0. (reworded commit)

* Update Gemfile.*
* Upgrade Rakefile to comply with new Rakefile format
Upgrade to bugfixed Padrino 0.11.1 release

(see padrino/padrino-framework#1179)
Merge pull request #34 from bascht/feature/upgrade-padrino

Update Padrino to 0.11.1