Switch to targetSdkVersion=21. b/16408109

Change-Id: I0b2a79e9ec0939d0702e82857f323d64f88c9d3a
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index a20f808..a083487 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -28,7 +28,7 @@
     <uses-permission android:name="android.permission.NFC" />
 
     <!-- This needs to be present when we are doing unbundled releases. -->
-    <uses-sdk android:targetSdkVersion="19" android:minSdkVersion="14" />
+    <uses-sdk android:targetSdkVersion="21" android:minSdkVersion="14" />
 
     <application
         android:icon="@mipmap/ic_launcher_mail"