Merge remote-tracking branch 'upstream/master' into HEAD

* upstream/master: (342 commits)
  Update TODO list
  Fix some rustc warnings
  Fix some Clippy warnings
  Rustfmt
  Another fix for stderr support
  Rustfmt
  Simplify surrogate pair handling on windows
  Fix on windows when using stderr.
  Allow customization of the output stream
  Ignore all IO errors during completion
  Prepare 2.1.0 release
  Fix line refresh/redraw (#149)
  [unstable] Fix error: scoped lint `...` is experimental
  Update TODO list
  Flag ReadlineError, Cmd, KeyPress as non exhaustive
  Improve key press handling
  Fix clippy warnings
  Rename consts.rs to keys.rs
  Prepare 2.0.1 release
  Windows: fix enable_raw_mode
  ...

Change-Id: I4a5ea48918ba09f93037b8cabdb259af9edab1f2