SMART-Response-XE-Arduino-Basic-Port

This is a port of Robin Edwards Arduino Basic for the SMART Response XE. In addition to his functionality I have added:

1. Batt: an operator that returns the voltage of the battery in mV (print batt, a=batt)
2. MSAVE/MLOAD: Saves current program to memory locations in external memory. There are 10 locations (0-9) These commands return the number of bytes stored or retrieved. (msave 6)
3. Bye: puts the unit into sleep mode. Current, 5mA operating, 30uA in sleep.
4. ATN: the c function atan to round out the trig functions.