- expose Host for (sub)domains.

server.go

 	return server
 }
 
+// Host creates a new application group under the given (sub)domain.
+func (self *server) Host(domain string) *server {
+	var middleware = new(middleware)
+  self.mux.Host(domain).Handler(middleware)
+  var mux = self.mux.Host(domain).Subrouter()
+
+	server := &server{middleware: middleware, mux: mux}
+	self.subservers = append(self.subservers, server)
+	return server
+}
+
 // Name returns route name for the given request, if any.
 func (self *server) Name(r *http.Request) (name string) {
 	var match mux.RouteMatch

server_test.go

 	})
 }
 
+func TestHost(t *testing.T) {
+	app := New()
+	app.Get("/", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("X-Powered-By", "base")
+	})
+
+  user := app.Host("localhost")
+	user.Get("/", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("X-Powered-By", "rex")
+	})
+
+	Convey("rex.Host", t, func() {
+    request, _ := http.NewRequest("GET", "http://localhost/", nil)
+		response := httptest.NewRecorder()
+
+		app.ServeHTTP(response, request)
+		So(response.Header().Get("X-Powered-By"), ShouldEqual, "base")
+
+		user.ServeHTTP(response, request)
+		So(response.Header().Get("X-Powered-By"), ShouldEqual, "rex")
+	})
+}
+
 func TestFileServer(t *testing.T) {
 	Convey("rex.FileServer", t, func() {
 		var (