2.1.0

CHANGES:

• Add TRMC (Tail Recursion Modulo Cons) support
  (#743)
• [playground]: Add melange.dom to bundle
  (#779)
• Fix Sys.argv runtime to match declared type
  (#791)
• Make 'a Js.t abstract (again), fixing a regression when bringing back
  OCaml-style objects BuckleScript
  (#786)
• Don't issue "unused attribute" warning for well-formed @@@mel.config in
  interface files (#800)
• Stop showing Js__.Js_internal in types and error messages
  (#798)
• Fix printing of OCaml-style objects and uncurried application
  (#807)