Remove gsutil specifics to make plugin reusable

[ktintc]

• Remove gsutil specific client_id and client_secret to make the plugin reusable by other apps. These credentials can be taken from the boto config or enviroment variables.
  • Remove gsutil specific comments.
  • Remove adding third_party libs to the path as we're installing them anyways.
  • Bumping up the version to 1.2 (accidentally got reverted in my previous change)

[jterrace]

Closing in favor of #3