Update CC3000.md

Clarified bit about VCC on the CC3k - I hope this is what you meant. 

Per https://forums.adafruit.com/viewtopic.php?f=19&t=51006 the Adafruit module includes a regulator that can take up to 18v - I think the bit about 2.7-4.8v was leading to confusion (with people trying to power the board off of the Espruino's 3.3v, which can't take it).