Added I2C Support

Added I2C support. This should obviously be peer reviewed. I tested using an 8x8 Matrix LED display. Results are identical for Arduino and BBB. I also threw together a quick demo for the TMP102 temperature module, and results are identical for Arduino and BBB. 

I am not sure if it worth providing tests for the 3 i2c methods, since there is no pin manipulation to test.
Not sure what you thoughts on this might be.
It's better to change this:
```js
    if (i2cError) {
      console.error("I2CReadERROR: error = " + i2cError);
      throw new Error("I2CRead Error");
    }
```
to this:
```js
    if (i2cError) {
        this.emit("error", i2cError);
        return;
    }
```