added a note about the controller factory in the docs (closes #558)
added a note about the controller factory in the docs (closes #558)

romainneutron/Silex,Xephi/Silex,lokhman/Silex,beealone/Silex,naderman/Silex,RayRutjes/Silex,CarsonF/Silex,tcx1000/Silex,lokhman/Silex,akucherevskiy/developex_test,GromNaN/Silex,JPry/Silex,cesarmarinhorj/Silex,Tobion/Silex,akucherevskiy/developex_test,silexphp/Silex,CarsonF/Silex,peterkokot/Silex,GromNaN/Silex,Incognito/silex-fork,plotek/Silex,SanderKnape/Silex,mathroc/Silex,beealone/Silex,tcx1000/Silex,GromNaN/Silex,jdreesen/Silex,Tobion/Silex,cgsmith/Silex,fabpot/Silex,Tobion/Silex,akucherevskiy/developex_test,plotek/Silex,fhinkel/Silex,naderman/Silex,naderman/Silex,mathroc/Silex,jdreesen/Silex,romainneutron/Silex,romainneutron/Silex,Incognito/silex-fork,cesarmarinhorj/Silex,arduanov/Silex,SpacePossum/Silex,arduanov/Silex,SanderKnape/Silex,mmauri04/Silex,peterkokot/Silex,mTorres/Silex,fhinkel/Silex,cgsmith/Silex,CarsonF/Silex,JPry/Silex,Xephi/Silex,peterkokot/Silex,gencer/Silex,mTorres/Silex,mmauri04/Silex,SpacePossum/Silex,fabpot/Silex,RayRutjes/Silex