New /roll command for 0.2.3 version

Okay, I updated my change for the new 0.2.3 version. 

Everything went well except I had to do a weird double if statement in the ChatServer.js (lines 203-209) perhaps because I don't fully understand coffee script. If you know of a better way of writing that I would appreciate knowing how.

Updated the README too, basically you can do /roll and get a d20. Or be more specific using any of the following formats: 20, d20, 1d20. Then you can roll multiple dice using 3d20. The multiple rolls use separate random numbers and show each separate roll like: 2 + 4 + 5 = 11. The rolls happen server side to prevent cheating client side. Then a message is sent to the client letting them know they rolled and one to the room letting the room know the results of the persons roll.