In your top-level build.gradle file you need to update the dependencies to use
classpath 'com.google.gms:google-services:1.5.0-beta2'
Extra Info:
The latest version of this can be found by looking at the entry on JFrog Bintray
Further Update:
Yes this has been updated since I answered the question. The latest version is:
classpath 'com.google.gms:google-services:3.0.0'
However, it’s always worth following the provided link to find the latest version.