Added a parent variable to a route so that it tells who its parent
controller was (if any).

If it doesn't have a parent it will be nil.

See motivation here:
https://github.com/dariocravero/padrino-autobind-parent-example
Added tests
Merge pull request #1097 from padrino/make-route-remember-parent

Added a parent variable to a route so that it tells who its parent controller was (if any)