exchanger v0.3.0

• Fixes error in Gibbs update for entity attributes and links
• Uses improved scaling for "temperature" of distortion softmax distribution
• Adds support for point mass priors on the distortion probabilities
• Adds support for a gamma prior on the concentration parameter associated with
  the distortion distribution
• Fixes bug in update for Pitman-Yor parameters

exchanger v0.2.0

• First release after major refactoring
• Depend on comparator and clevr for distance functions and evaluation functions respectively
• Use underscore_case instead of camelCase for function/variable names
• Implement show methods for user-facing objects
• Improve quality of documentation