Re-enable Proguard, supports 3D all apps correctly now.

Change-Id: I84ab56054c9f57985fec9107c3977691177b85a4
diff --git a/proguard.flags b/proguard.flags
index fb145aa..5d72ef3 100644
--- a/proguard.flags
+++ b/proguard.flags
@@ -3,4 +3,6 @@
   public void nextScreen(android.view.View);
 }
 
--keep class com.android.launcher2.AllApps3D.Defines
+-keep class com.android.launcher2.AllApps3D$Defines {
+  *;
+}