Slack pinging

[DumboOctopus]

So for buzz, users can sting another. Buzz will send a slack message the stinged user "You have been stung by [other user]".

~We want to do something similar for meow. Meow posts can have tags but tags are optional. Unfortunately, this means that many people have not tagged their posts. So this task will be to sting the last edit user if the post has not been tagged and it has already been sent.~

actually, the above idea might be a bit too much for our first use of stinging. So instead, whenever a meow errors, we will slack message @nprajapati so that he knows he should go check the logs.