[docs] Satisfied golint.

- SkipRouter should also be ErrRouterSkipped (or similar) but a change would
  break the public API.

mux.go

@@ -236,7 +236,7 @@ func (r *Router) Schemes(schemes ...string) *Route {
 	return r.NewRoute().Schemes(schemes...)
 }
 
-// BuildVars registers a new route with a custom function for modifying
+// BuildVarsFunc registers a new route with a custom function for modifying
 // route variables before building a URL.
 func (r *Router) BuildVarsFunc(f BuildVarsFunc) *Route {
 	return r.NewRoute().BuildVarsFunc(f)