Cooldown period for public commands.

[dougarley]

Commands like !votejarski could be publicly available if they can have a global cooldown period (like once every 30 minutes unless by an admin, etc).

If the command is on cooldown users could receive feedback in a DM (per #275) on the length of the cooldown period.

[fusion2004]

To what level should we store & enforce this cooldown? Please pick one!

1. Global
2. Guild (ThaSauce Community)
3. Channel
4. User who triggered the command

[dougarley]

What would effectively be the difference between global and guild? Like, if the bot is on multiple servers? In that case I would guess guild would be appropriate.