First pass at AdaFruit Motor Shield v1.*

This is my first attempt at implementing an AdaFruit motor shield with directional control.

Hoping to see if I am on the right track before I finish this up (tests, documentation, etc).  

You can create a motor the traditional way with the controller:

```javascript
new five.Motor({
  pins: { pwm: 11 },
  controller: "ADAMOTOV1"
});
```

But since these motors are called out by name and it can be hard to find the documentation which tells us which PWM pin to use for which motor, I built it into the configuration of the controller:

```javascript
new five.Motor({
  name: "M2",
  controller: "ADAMOTOV1"
});
````

Thoughts?
Putting this method on the motor instance means that this motor instance looks different from other motor instances—all instances of Motor should have the same surface (exposed properties, methods). Once `bits` are moved into the private state table, the `updateShiftRegisters` function will no longer be this-sensitive and can be just a plain function in the module's scope.