Principe of reactToAMQPMessage() changed - callback removed.

It now returns the values, instead of calling callback function. This makes
things easier in other moduless. Also, I have no idea, why I designed it
like that.

Docstring updated little bit.
Tests updated to reflect changes in reactToAMQPmessage().
Documentation massively updated and rewritten. Fixes #11.
Package version/information updated.