Stop an app from showing up in the play store updates

I've got a very old version of the facebook app that I use. I find it works very well for me, but due to it's age, whenever I check my updates, it's always there. I'd love to just be able to hit update all, and not worry about facebook updating. Is there any way I can do this? Basically remove it from that list. I know I've read here and there about re signing it or something, but I can't seem to figure it out. Any help is great!