Added Teensy ADC to Serial sketch.

It maps all joystick directions to digital values, amps the new switch
to enable command, and maps all four pots to analog values.  It uses a
hysteresis of 100 which gives us roughly 10 slots.  Not ideal but
stable.

Changed Serial code to properly map incoming analog values to effects.
First analog controller is now rerouted to speed but I'm also now
mapping the UP/DOWN joystick buttons to two new values for effects for a
total of five inputs.

Added setSpeed(float) method on efffect_runner class to allow us to
change speed midstream.  It was previously implemented as a command
flag.