added a comment
in class TreeProcessor: added support for "spectator variables"
factored out ROOT specific code from method TreeProcessor.makeTree(..) to a new class _RootTreeWriter
factored out a new method _makeOutput(..) from method makeTree(..) in class TreeProcessor
in method TreeProcessor._makeOutput(..): fixed looping over range of events
added support for returning result in method TreeProcessor._makeOutput(..)
factored out numpy specific code from method TreeProcessor.makeArray(..) to a new class _NumpyArrayMaker