Add savedInstanceState to drawer

src/main/scala/com/github/shadowsocks/MainActivity.scala

@@ -203,6 +203,7 @@ class MainActivity extends Activity with ServiceBoundContext with Drawer.OnDrawe
       )
       .withOnDrawerItemClickListener(this)
       .withActionBarDrawerToggle(true)
+      .withSavedInstance(savedInstanceState)
       .build()
 
     val header = drawer.getHeader
@@ -364,6 +365,11 @@ class MainActivity extends Activity with ServiceBoundContext with Drawer.OnDrawe
     super.onStop()
   }
 
+  override def onSaveInstanceState(outState: Bundle) {
+    super.onSaveInstanceState(outState)
+    drawer.saveInstanceState(outState)
+  }
+
   override def onDestroy() {
     super.onDestroy()
     app.settings.unregisterOnSharedPreferenceChangeListener(this)