feat: add callback to i2c constructor

[matheussampaio]

Add a optional callback to I2C constructor.

const i2c = new I2C(DEFAULT_DDCCI_ADDR, { device: '/dev/i2c-1' }, (error) => {
  if (error) {
    console.error(error);
  } else {
    console.log('success');
  }
});

[matheussampaio]

This closes Issues #76.

[rzr]

Looks good, an other option would be to align iotjs i2c.open API :
https://github.com/jerryscript-project/iotjs/blob/master/docs/api/IoT.js-API-I2C.md

[rzr]

May I suggest to consider to forward to abandonware fork

Relate-to: #97