WIP. Add route helper & notify of deprecation

It's a bit presumptuous to add a route at the tail end of a route map -
which is what we're doing currently - so, instead, we should provide an
easy manner to add the route wherever. The route extension should
accomplish that.

Added a post install message in the gemspec to notify users that they
should make sure to add the route manually or w/the helper.
Update README