Added

• Added the ConstantKeyword, RankFeatures field types (#1456, #1465)
• Added the ScriptScore query type (#1464)
• Added UpdateByQueryResponse.success() method (#1463)
• Added return_doc_meta parameter to Document.save() and Document.update() for
  accessing the complete API response (#1466)
• Added support for calendar_interval and fixed_interval to DateHistogramFacet (#1467)
• Added Document.exists() method (#1447, contributed by @dem4ply)
• Added support for the year interval to DateHistogramFacet (#1502, contributed by @nrsimha)

Fixed

• Fixed issue where to_dict() should be called recursively on Search.extras and **kwargs (#1458)
• Fixed inverse of an empty Bool query should be MatchNone (#1459)
• Fixed issue between retry_on_conflict and optimistic concurrency control within Document.update() (#1461, contributed by @armando1793)