Update Walk to match all subrouters

Matches all routes instead of just routes with paths.

Fixes #261

mux.go

@@ -299,10 +299,6 @@ type WalkFunc func(route *Route, router *Router, ancestors []*Route) error
 
 func (r *Router) walk(walkFn WalkFunc, ancestors []*Route) error {
 	for _, t := range r.routes {
-		if t.regexp == nil || t.regexp.path == nil || t.regexp.path.template == "" {
-			continue
-		}
-
 		err := walkFn(t, r, ancestors)
 		if err == SkipRouter {
 			continue