I got a corny keg for Christmas, and am not sure what else I need to get going. I was looking at the a keg system at Midwes Supplies (http://www.midwestsupplies.com/cornelius-keg-system-with-5-lb-co2-tank-comes-empty.html) but all it says in addition to the keg, CO2 bottle, regulator and tap is...