Set Emacs dependency to 24.4

Magit depends on us and this is the Emacs version it supports. This is
still a recent enough version to remove the called-interactively-p
workaround.

ido-completing-read+.el

@@ -6,7 +6,7 @@
 ;; Author: Ryan Thompson
 ;; Created: Sat Apr  4 13:41:20 2015 (-0700)
 ;; Version: 4.0
-;; Package-Requires: ((emacs "25.0") (cl-lib "0.5"))
+;; Package-Requires: ((emacs "24.4") (cl-lib "0.5"))
 ;; URL: https://github.com/DarwinAwardWinner/ido-ubiquitous
 ;; Keywords: ido, completion, convenience