Add "types" to path matchers about metal-plugins

[jbalsas]

Copied from deprecate/metal-router#24 by @jbalsas

Hey @mthadley, this does indeed seem interesting, but I haven't been able to find a similar approach out there int he wild. All of them seem to just rely on regexes for this.

I'd be more comfortable if there is already a pattern for this out there, so we don't need to come up with our own format. Do you know of any such cases?

[jbalsas]

Copied from deprecate/metal-router#24 (comment) by @mthadley

@jbalsas Yea! So Django recently added something like this. Check it out here.

[jbalsas]

Copied from deprecate/metal-router#24 (comment) by @Robert-Frampton

This would actually mean changing Senna and https://github.com/metal/metal-path-parser.

@brunobasto, what are your thoughts on this behavior for the Senna Route class?

[brunobasto]

Hey guys, I might have missed this thread. I like the idea. If everyone agrees, we can try to add support for it. We should probably do it in way that's backwards compatible thought.