Improves ido-recentf-open

Two main improvements over the old version:
* Expands ~ to your home directory
* Doesn't have the bug preventing you from opening your most recent file (if you press C-x f then enter with the old version, it barely ever works)

Written by Steve Purcell:
http://www.reddit.com/r/emacs/comments/21a4p9/use_recentf_and_ido_together/cgc8f6b