A small demo how to use Retrofit to retrieve an OAuth2 access token from a Google account and use it to read the user's Google profile.

1. create a new project: console.developers.google.com, and go to
   • APIs & auth
     • Credentials
       • Create New Client ID
       • Installed application and Other
       • Create Client ID
       • copy the Client ID and Client secret
     • APIs
       • enable Google+ API
2. create a file called local.properties in the root of this project and add the keys client_id and client_secret to it (and the corresponding values from step 1, of course)
3. run the main class by executing mvn exec:exec, and follow the instructions on the console