Use OpenID for Google and Yahoo authentication

This maintains compatibility with existing accounts until we can figure
out an upgrade path to OAuth2 for these services.
Update provider name for LinkedIn
f google yahoo openid
Re-add Mogli for Facebook API lookups
Switch to updated fork of omniauth-foursquare for user names and bios
Always use info from auth hash to create people from Twitter, GitHub, and Foursquare
Bring Gemfile.lock up to date with other commits
Fix AuthProbe: remove Twitter, update GitHub API