use gorilla/mux for routing requests

Thanks to @Fieldistor for the reminder that gorilla/mux allows you to
disable cleaning request URLs, which was causing problems with signature
verification for some URLs.

Fixes #215
Fixes #212

cmd/imageproxy/main.go

@@ -31,6 +31,7 @@ import (
 	"github.com/die-net/lrucache"
 	"github.com/die-net/lrucache/twotier"
 	"github.com/garyburd/redigo/redis"
+	"github.com/gorilla/mux"
 	"github.com/gregjones/httpcache/diskcache"
 	rediscache "github.com/gregjones/httpcache/redis"
 	"github.com/jamiealquiza/envy"
@@ -99,9 +100,10 @@ func main() {
 		Handler: p,
 	}
 
+	r := mux.NewRouter().SkipClean(true).UseEncodedPath()
+	r.PathPrefix("/").Handler(p)
 	fmt.Printf("imageproxy listening on %s\n", server.Addr)
-	http.Handle("/", p)
-	log.Fatal(http.ListenAndServe(*addr, nil))
+	log.Fatal(http.ListenAndServe(*addr, r))
 }
 
 type signatureKeyList [][]byte