Add the macro style router definition?

[pepe]

As can be seen here https://github.com/zizkovrb/rustmvc/tree/macro-router.

Experimental compiler feature must be enabled (from what I gather anyway ;).

[steveklabnik]

I'd be interested in pulling this in eventually, but you're right: macros are an unstable feature. I'd like to get things actually done first, and then add stuff like this at the end, I think :)