Fix Rakefile problem "rake/rdoctask is obsolete"

Full error:

rake aborted!
ERROR: 'rake/rdoctask' is obsolete and no longer supported. Use 'rdoc/task'
(available in RDoc 2.4.2+) instead.
/home/void/Coding/padrino-responders/Rakefile:53:in `<top (required)>''`
Bumped dependencies for padrino and rack-flash (now using rack-flash3)
The request no longer has a route, fix controller and action retrieval

The current git version of padrino puts the action in the request, too, but we
have to do some vodoo to get it otherwise.