Converts img tags with a URL based SRC tag to an anchor tag to protect against an invisible DOS (Sending a huge image in the src tag).
Big thanks to Ilari Lind who's urltoimg.py plugin this plugin is based on. See https://github.com/Aciid/urltoimg-for-mumo for details.
Also thanks to @frecel for pointing this plugin out to me.