this test takes in a digital input and outputs a PWM that will control a servo. The servo should go to it's "maximum" position when the button is pressed and to its "minimum" position when it is released

circuit setup:
connect a pushbutton between pin 18 and 3.3v. A pull down resistor is optional.
connect a hobby servo's power supply wires to 5 V and ground, and the signal wire to pin 20.
