add _matchedRouteName to context

[netroy]

sometimes route paths can be very long & convoluted (legacy apis), exposing the layer
name provides a saner alternative for analytics

this is an extension to #236

/cc @alexmingoia @jergason

[jergason]

Is there a reason to make this backwards-incompatible? Why not have both the route and the name?

[netroy]

@jergason it is backwards-compatible.. the _matchedRoute property is still there

[jergason]

Ah crud, I read it too quickly. Thanks for correcting me.

[netroy]

/cc @jbielick

[Mousius]

I was looking for something along these lines to identify the route for stats purposes. In #341 it was suggested to use _matchedRoute but that's not quite as clean for a stats counter. If these things are features they should be documented and not considered private. Maybe adding ctx.routePath and ctx.routeName as well as the backwards compatible ctx._matchedRoute?