To use this script, you'll need to install the Tampermonkey extension or Violentmonkey extension for your browser first, available here:
http://www.tampermonkey.net/ http://violentmonkey.github.io/
Simply install the extension, then click the "Install" button on this page. (The extension will show you the script's contents before giving you the option to install it.) That's pretty much it! The extension will only enable the script on the appropriate page, and update the script when and if I make updates here (though it will check with you before each update of course).

Unfortunately this script doesn't seem to work with Greasemonkey, probably because of this issue: https://github.com/greasemonkey/greasemonkey/issues/2700