No instructions on how to run prometheus and dash together

[mattcolegate]

Raising on behalf of @seabaylea
At the moment the documentation in the README is sufficient to run either SM-dash or SM-prometheus. The only documented constructors in the example are the convenience ones, so each will create their own Router and pass it to Kitura. This means the last one created wins, and will block the other from displaying.

Documentation needs to show how to create and pass a Router object to SM-dash and SM-prometheus constructors so that the two can co-exist on the same Kitura server.