add http verbs methods to Router

By having the method verbs available on the router, users can set up
disjoint routers and organized paths easier.

It is now possible to have a .js file export the router.middleware and
attach these paths using an `app.use('/path', middleware)` call. This
means that any routes written in the separate file do not need to have a
full path hardcoded as they can be mounted by the application anywhere.

This is already possible using `router.route(verb, args)` however is
needlessly verbose without this patch.