Ye olde favourite /roll command from WoW chat, with some dnd flavour

Supports following modes of usage:

• /roll NdS rolls a dice, where N is number of times to roll, S is number of sides.

• /roll d6 rolls one d6, same as rolling 1d6

• /roll d6, 2d4 rolls one d6, followed by two rolls of d4

• /roll NUMBER rolls a random number in the 1 to NUMBER range

• /roll NUMBER-NUMBER rolls a number in the specified range: (a, b) => roll(diff(b, a)) + a; should look for the first dash after trimming and skipping first symbol, split and parse int.

• /roll rolls a classic 1-100 roll.