Middleware uses :path-info as well as :uri

* When running a Ring app in a servlet environment, :uri contains the path of the app, but it also includes the servlet base path. This causes problems with route matching since it currently only uses :uri.
* 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
Merge pull request #16 from mwmitchell/master

Middleware uses :path-info as well as :uri