Application: Fix deprecated Gtk.Application.add_accelerator (#94)

Author: ryonakano

src/Application.vala

@@ -64,7 +64,7 @@ public class Eddy.Application : Gtk.Application {
 
         var quit_action = new SimpleAction ("quit", null);
         add_action (quit_action);
-        add_accelerator ("<Control>q", "app.quit", null);
+        set_accels_for_action ("app.quit", {"<Control>q"});
         quit_action.activate.connect (() => {
             if (window != null) {
                 window.close ();