Add support for referencing synonym routes

[jwyuen]

What I mean by this is sometimes you have two different routes that are essentially the same thing. For example:

GET class/{classId}/student/{studentId}

GET student/{studentId}

Instead of duplicating api doc code, you could just reference the other existing route.

[webron]

@jwyuen - there's a problem here, specifically with your example. Your example shows that the first path has two path params and the second one has a single path param. How would you refer one to the other?

[webron]

Closing this in favor of #213. Feel free to provide more information there.