Prepare for release.

Author: athas

Changelog

@@ -1,12 +1,10 @@
-Changed in version UNRELEASED:
+Changed in version 0.8.4.0:
 
    * On Windows, when terminal-style and printing output, no longer skips
      `"\ESC...\STX"` sequences. (If used with legacy ConHost directly (for
      example, `conhost.exe cmd.exe`), it will require ConHost's ANSI-capability
      to be enabled separately.) (#126)
 
-Changed in version 0.8.4.0:
-
    * Added `System.Console.Haskeline.ReaderT` module for `ReaderT` interface.
 
    * `System.Console.Haskeline.Completion.listFiles` now returns a sorted list.