Spotlight and Markdown Files

Hello,

I run a few websites and as a result have a large amount of files that end in .markdown. I've recently noticed that spotlight does not index these files. Is there anyway to tell spotlight to index their content? They are really only txt files, but end in .markdown so that textmate knows what to do with them.

Thank you in advance for any help,

-Grey
http://www.silverclipboard.com/