Fix Rakefile problem "rake/rdoctask is obsolete"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ERROR: 'rake/rdoctask' is obsolete and no longer supported.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.
Version bump to 0.1.6
Merge pull request #5 from voidus/master

Make padrino-responders work with latest padrino