• Maxwell will now include by default fields with NULL values (as null
  fields). To disable this and restore the old functionality where fields
  were omitted, pass --output_nulls=false
• Fix an issue with multi-client support where two replicators would
  ping-pong heartbeats at each other
• Fix an issue where a client would attempt to recover a position from a
  mismatched client_id
• Fix a bug when using CHANGE COLUMN on a primary key