CLC-3641 Migrating to new Google+ API

https://jira.ets.berkeley.edu/jira/browse/CLC-3641

Use the G+ API to get user's email. This does NOT require revocation of existing auth tokens. 

Please wait for green Bamboo: https://bamboo.ets.berkeley.edu/bamboo/browse/MYB-CLCMVPCHRIS2-3