Dialog based communicator back end

Wrote a `dialog` based communicator implementation, using the `mixed gauge` dialog: 

![screenshot from 2014-12-03 03 26 50](https://cloud.githubusercontent.com/assets/2464627/5274994/cbd934b4-7a9d-11e4-986d-984ab1bded41.png)
![screenshot from 2014-12-03 03 27 29](https://cloud.githubusercontent.com/assets/2464627/5274995/d328d030-7a9d-11e4-9e21-81e8c79852dd.png)

The overall percentage is currently only a hack / guess, but you could look into it later maybe for a better estimate

This would of course add `dialog` to the dependency list, so that should be updated as well