4.0.0: API changes

BREAKING CHANGES

• Top level export Chemin now only contains isChemin, parse and create
• Other function have been moved to methods on Chemin object
  • serialize (third parameter option added to control leading / trailing slash)
  • match
  • matchExact
  • extract
  • toString (previously stringify)
• CheminParams have been renamed CheminParam (without s)
• In Chemin.parse foo? now resolved to a new CheminParam.optionalString changing the type of it's value

v3.0.1...v4.0.0