Status Callback Function

I added a status callback function which is called on different status changes. It's easily to extend and use. All you have to do is to add a callback function to the options.

These status will be current supported:

OTR.Status = {
    SEND_QUERY: 0,
    AKE_INIT: 1,
    AKE_SUCCESS: 2,
    SMP_INIT: 3,
    SMP_RECEIVE_SECRET: 4,
    SMP_ANSWER: 5,
    END_OTR: 6
  }

I gave a short example function in the readme.

regards