Instead of com.google.android.gcm:gcm-server, com.ganyo:gcm-server could be used, which is available on Maven Central: http://search.maven.org/#search%7Cga%7C1%7Ca%3A%22gcm-server%22

This change will make possible to remove GCM related repository from our UPS implementation. Both files are almost the same content-wise, the only difference is Message.Builder containing setData(Map) as well as addData(String, String) for Maven Central hosted implementation.

Removing dependency on github repository increases probability of build being reproducible in future.