Version 0.20.0

   +  Refactored ``experiments`` module to remove unnecessary child processes,
      and greatly simplify ablation code. This should fix issues #73 and #49.
   +  Deprecated ``run_ablation`` function, as its functionality has been folded
      into ``run_configuration``.
   +  Removed ability to run multiple configuration files in parallel, since
      this lead to too many processes being created most of the time.
   +  Added ability to run multiple ablation experiments from the same
      configuration file by adding support for multiple featuresets.
   +  Added ``min_feature_count`` value to results files, which fixes #62.
   +  Added more informative error messages when we run out of memory while
      converting things to dense. They now say why something was converted to
      dense in the first place.
   +  Added option to ``skll_convert`` for creating ARFF files that can be used
      for regression in Weka. Previously, files would always contain non-numeric
      labels, which would not work with Weka.
   +  Added ability to name relation in output ARFF files with ``skll_convert``.
   +  Added ``class_map`` setting for collapsing multiple classes into one
      (or just renaming them). See the
      [run_experiment documentation](http://skll.readthedocs.org/en/latest/run_experiment.html#input) for details.
   +  Added warning when using ``SVC`` with ``probability`` flag set (#2).
   +  Made logging much less verbose by default and switched to using
      ``QueueHandler`` and ``QueueListener`` instances when dealing with
      multiple processes/threads to prevent deadlocks (#75).