While trying to install the extension on our machine (Ubuntu 16, MW 1.29) both with branch 1.29 and master. Looks like it does not find the Api client Library (Composer installed inside extensions' directory). This is the exception when using the master:
Error from line 203 of /path/to/wiki/w/extensions/GoogleAnalyticsMetrics/GoogleAnalyticsMetrics.hooks.php: Class 'Google_Service_Analytics' not found
Note that this is talk by @Wess: originally posted to the extension's page.