Fix rubygems/travis badges and links.
Fix rubygems/travis badges and links.

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