Enable proguard

Change-Id: I5a9fb731633ced3aa415b95d44fe2995981c9a52
diff --git a/proguard.flags b/proguard.flags
new file mode 100644
index 0000000..c4af490
--- /dev/null
+++ b/proguard.flags
@@ -0,0 +1 @@
+-verbose