Can subscribe after joining game (solo-game view)

Addresses #39
Holding off on closing #39 until #58 is addressed.
Initialize admins. Allow admins to edit games.
Offer subscription after adding + joining game
Avoid duplicate (overlapping) region subscriptions

Also, show subscription region on map in search view.
Concerns #58
Fix method of determining region intersection

Applies to #58
Notify added friend via email
Invite friends via forwarded email, not form input

Close #61
Use showdown core package rather than custom import
Remove transformation of Games - keep them as EJSON
Refactor `displayTime` as pure function in utils
Stop gameAddedNotifier - should implement daily digests
Merge branch 'devel'