Python3 and rfthermtest.py changes

[carlpe...@icloud.com]

Here are the changes to rfthermtest.py to run with python3.

line 37: print("Please wait max 5 mins for the temperature transmitter to transmit...")

line 42: char = ser.read().decode('ascii')

line 50: llapMsg += ser.read(11).decode('ascii')

line 56: print("Device Number : " + devID)

line 57: print("Temperature data : " + data)