(TK-44) Webrouting Documentation

This PR adds documentation for the webrouting service as well as an example webrouting application.
I think it's worth adding a paragraph up here somewhere that describes the intent of this service.  Here's a rough stab at it:

```
The Web Router Service is an optional service that gives you a different way to manage the configuration of your web service URLs.  If a TK web service registers its endpoints directly with the TK Webserver Service, then it's possible that you may end up with these endpoint registrations being a bit scattered around your code base, and that can make it hard to reason about what endpoints might be running in your server (and which TK services registered the endpoints).

The Web Router Service is a thin wrapper around the Webserver Service which allows you to consolidate all of your URL configuration into a single section of your trapperkeeper config.  For example:

<insert sample config here>

The services in the configuration above would be written to use the Web Routing Service to register their web endpoints, rather than using the Webserver Service directly.  Then, developers/users/administrators can simply reference this one section of the configuration to determine that there are web endpoints registered at 'foo', 'bar', and 'baz', and that these endpoints are registered in the clojure namespaces 'foo.bar' and 'foo.baz', accordingly.
```