Middleware uses :path-info as well as :uri

* When running a Ring app in a servlet environment, :uri contains the full path of the app – which includes the servlet base path. This causes problems with route matching when your root route starts with / – because bidi currently only uses :uri. The :path-info value on the other hand, is the path, but without the servlet base path.
* This is similar to what Ring already does with the path-info fn here: https://github.com/ring-clojure/ring/blob/1d74427381b2861639033ab80007b6bbef1be508/ring-core/src/ring/util/request.clj#L54
* Added simple test