Add initial skeleton code for plugin that grabs authentication token from the GCE metadata server and writes logs to stdout.
Add initial skeleton code for plugin that grabs authentication token from
the GCE metadata server and writes logs to stdout.

hakobera/fluent-plugin-google-cloud,GoogleCloudPlatform/fluent-plugin-google-cloud,senthilkumar-kj/fluent-plugin-google-cloud,laramiel/fluent-plugin-google-cloud,cosmo0920/fluent-plugin-google-cloud,arthurdarcet/fluent-plugin-google-cloud,brint/fluent-plugin-google-cloud,swalkowski/fluent-plugin-google-cloud,a-robinson/fluent-plugin-google-cloud,mururu/fluent-plugin-google-cloud