Slack-to-uid.md

 Someone is going nuts on the cluster, or you just want to contact them on Slack.
 Unfortunately many of us picked slack @names unaware of how hard it is to link a uid to a slack id.
 
-epd -- pdoak  
+epd -- epd  
 wl6 -- weili  
-rbala -- rbala  
 pk7 -- paulrckent  
 f9y -- fmyuan