Added custom Filter.

Hi there, as I just wrote a TS3 Viewer I had the problem to use the cid inside the client to display the channel in an easy and smart way. As I didn't found another way to do it with current possibilities (a new filter was no choice for me as it is some kind of normalisation and I use GameQ in a very generalized way) I added the possibility to return a callable form the protocol, which defines Protocol specific normalisation which can not be created with the current system. 

Hope you'll like it and add it to your repo.

EDIT: Somehow the Exception fix #60 also got pushed... I am not so familiar with the Github interface...