CommandHandler fix
Merge pull request #35 from Miliooo/loop

CommandHandler avoid endless loop
Implementing Aggregate Factory

This work is comprised of changes from both @simensen and @kelvinj and taking
into account a lot of discussion on IRC. Squashed 7 commits into one.
Change ordering of aggregate factory argument and make it mandatory.
Merge pull request #44 from simensen/aggregate-factory

Aggregate factory