quests->[un]invite methods
/invite and /uninvite methods in api
invite and uninvite actions on frontend
quests->invite checks if user exists
quest completion adds points to everyone
team-quests: frontend experiments
move quest action buttons to the left; invites; etc.
Merge branch 'master' into team-quests

Conflicts:
	www/models/quest.js
more css improvements
quest->invite doesn't allow to invite team member
clear invitee list on quest status upadtes; forbid joining non-open quests
frontend: clear unused console.log
test non-open join/invite behavior
quest-invite events
invite email notifications
starting to implement responsive quest page
quest-page: separate all @media styles
responsive quest page - "good enough"
jasmine tests: mock mixpanel
fix jasmine tests