api: Update readme re: android SDK https://codereview.appspot.com/7447043/
api: Update readme re: android SDK
https://codereview.appspot.com/7447043/

wgpshashank/google-api-java-client,ejona86/google-api-java-client,googleapis/google-api-java-client,palaniyappanBala/google-api-java-client,skinzer/google-api-java-client,rajesh-frontendengineer/google-api-java-client,wonderfly/google-api-java-client,ejona86/google-api-java-client,skinzer/google-api-java-client,SunghanKim/google-api-java-client,googleapis/google-api-java-client,wgpshashank/google-api-java-client,googleapis/google-api-java-client,SunghanKim/google-api-java-client,googleapis/google-api-java-client,r351574nc3/google-api-java-client,wonderfly/google-api-java-client,r351574nc3/google-api-java-client,palaniyappanBala/google-api-java-client,rajesh-frontendengineer/google-api-java-client