Fixed more infoGain bugs and made the applyInfoGain method more
efficient. Also added an applyInfoGain method which takes a single
instance and applies the infoGain for use on parallelized instance
objects. This is not used locally, and is intended for use on the
clusters. This version of applyInfoGain also does not return the double
array that the Instances version does (at least not at the moment. It
could be modified to do so if need be).