Rename `firmata` => `io`

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>
dreams of destructuring

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>
trivial nit

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>
Rename led `pinMode` => `mode`. Adds tests for auto mode switching

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>
Initial Servo unit tests

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>