Have Humbot use the (unsupported, alpha) Humbug receive-messages API.

Humbug is not yet officially supporting the receive-messages API,
and it will likely soon change, but using it is admittedly better
than the alternative.

This requires python-humbug 0.1.4~hackerschool, available at
https://humbughq.com/dist/api/python-humbug_0.1.4~hackerschool.tar.gz