This plugin relies on Twitter Toolsby Alex King. You must install that plugin to take advantage of sending your URLs to Su.pr.
This plugin is based off code from Viper007Bond, from the WordPress Plugins site – in fact it’s pretty much a direct rip of his/her work! Because of the very slight change to the API, I’ve only had to change a few things to make this work.
**Updated to fix a bug with authenticating login/API key 09/07/15