fixing issue with refresh token. Tokens are not refreshed when they are ...

This patch is to fix the issue with google drive tokens expiring and not renewing them automatically. 

The patch is in reference to oauth issue https://github.com/intridea/omniauth-oauth2/issues/40 and stackoverflow question http://stackoverflow.com/questions/12572723/rails-google-client-api-unable-to-exchange-a-refresh-token-for-access-token 

Let me know if you have any questions