Add Drop impl for Notification

The notification is now unrefed via the GObject system.

Cargo.toml

@@ -16,5 +16,6 @@ libnotify-sys = "^0.5.0"
 gdk-pixbuf = "^0.1.3"
 gdk-pixbuf-sys = "^0.3.4"
 glib-sys = "^0.3.4"
+gobject-sys = "^0.3.4"
 gtypes = "^0.2.0"
 glib = "^0.1.3"

src/lib.rs

@@ -26,6 +26,7 @@
 
 #[macro_use]
 extern crate error_chain;
+extern crate gobject_sys;
 extern crate gdk_pixbuf;
 extern crate gdk_pixbuf_sys;
 extern crate glib;
@@ -91,6 +92,23 @@ pub struct Notification {
     handle: *mut sys::NotifyNotification,
 }
 
+impl Drop for Notification {
+    fn drop(&mut self) {
+        unsafe {
+            if gobject_sys::g_type_check_instance_is_a(
+                self.handle as *mut gobject_sys::GTypeInstance,
+                gobject_sys::G_TYPE_OBJECT,
+            ) == FALSE
+            {
+                panic!("Not a GObject!");
+            }
+            let gobject = self.handle as
+                *mut gobject_sys::GObject;
+            gobject_sys::g_object_unref(gobject);
+        }
+    }
+}
+
 impl Notification {
     /// Creates a new Notification.
     ///