SciKit-Learn Laboratory (SKLL) 0.28.0

This release has some big behind-the-scenes changes. First, we split the data.py module up into a sub-package (#147). There is also a new FeatureSet class that replaces the old namedtuple-based ExamplesTuple (#81), so ExamplesTuple is now deprecated and will be removed in SKLL 1.0.0. Speaking of which, we're having an all-day SKLL sprint on the October 17th where we hope to resolve all the remaining issues preventing the 1.0 release. Other changes include: Fixed a bunch of minor problems with loading/writing LibSVM files Added file reading/writing progress indicators Fixed crash with generate_predictions when the model was not trained with probability set to True (#144). Deprecated write_feature_file function in favor of using a FeatureSetWriter object. Deprecated load_examples function in favor of using a Reader object. Temporarily added replacement version of scikit-learn DictVectorizer class until scikit-learn/scikit-learn#3683 version is included in a release. This allows us to make file loading substantially more memory efficient