GoogleStrategy should allow custom scopes

[agcty]

Describe the bug

Right now, the Google Strategy only allows for the "openid", "profile" & "email" scopes, however, there are many custom scopes that can be used with Google such as "https://www.googleapis.com/auth/business.manage" or "https://www.googleapis.com/auth/plus.business.manage". I propose changing the GoogleScope type to a simple string.