Version 0.4.7

• Tests Python3.7.
• Fixes #87: better handling of Conjunctions when adding them to the
  configuration space.
• MAINT: Improved type annotation in util.py which results in improved
  performance (due to better Cython optimization).
• MAINT: util.get_one_exchange_neighborhood now accepts two arguments
  num_neighbors and stdev which govern the neighborhood creation behaviour
  of several continuous hyperparameters.
• NEW #85: Add function to obtain active hyperparameters
• NEW #84: Add field for meta-data to the configuration space object.
• MAINT: json serialization now has an argument to control indentation