adds method for explicitly retrieving the access token,

The current implementation hides the QueryAccessToken method and only allows to get the access token via the GetUserInfo method.

Furthermore, the google client *requires* access to the 
https://www.googleapis.com/auth/userinfo.profile and https://www.googleapis.com/auth/userinfo.email scopes for successfully calling GetUserInfo w/o getting an exception. I believe that's asking for too many permissions that might not bee needed by the client.

Hence the GetToken provides an explicit way to retrieve the access token.

Other than that, the library is a pleasure to work with, kudos!