Correcting a few issues in the ControllerFactory

The DefaultControllerFactory handles throwing errors when it doesn't know what to do or the controllerType is null, and it's message is properly localized, so it makes more sense to allow it to handle this situation than to double-implement that. 

This change lets users of this nuget package avoid having to add route ignores for all URLs not handled by the controller factory to avoid debugger breaking (eg. favicon.ico as mentioned in the comments here: http://docs.castleproject.org/(S(kwaa14uzdj55gv55dzgf0vui))/Windsor.Windsor-tutorial-part-two-plugging-Windsor-in.ashx?Discuss=1).

Also fixed a spelling error in the readme.