shorter links

[afeld]

If an invite link need to be typed out (because it's being shared up on a projector, for example), the 32 character key is a bit of a pain. Two options:

• Shorten URL via a 3rd-party service – I sent a message to the bitly API discussion group asking if there's a way to do this without OAuth
• Use shorter keys, via the base62 gem (or similar)