Create se_grace_timer.user.js

This is a Stack Exchange user script that replaces "Edited n mins ago" with a timer for the first 5 minutes.  Stack Exchange allows revising a new post or an edit for 5 minutes without adding to the revision count in the revision history.  It's desirable to avoid having too many revisions, as questions and answers with more than 9 edits get converted to Community Wiki posts, and upvotes no longer earn the original poster karma.  Having a timer allows you to see whether you have time to make that one final tweak to your post while pretending you didn't.