Changelog for foldl-transduce-0.1.2.1

# 0.1.2.0 - Added explicit bifunctors dependency. - Added Transduce', TransduceM' type synonyms. - Added groups', groupsM'. # 0.1.1.0 - Changed signatures of transduce' and transduceM'. - generalize' -> generalizeTransducer - simplify' -> simplifyTransducer - dropped direct profunctors dependency.