• Removed support for Python 2.6 and 3.3
• Removed support for Django versions before 1.11
• Removed SkipPredicate exception and skip method of Predicate
• Removed replace_rule and related APIs
• Added set_rule and related APIs to safely replace a rule without having
  to ensure one already exists
• Added compatibility with Django v2.1
• Re-introduced support for PyPy and PyPy 3
• Changed Python and Django supported versions policy to exclude end-of-life
  versions. Support for EOL'd versions will be dropped in minor version
  updates of rules from now on.