so i was going around my outpost when i saw a skeleton horse, when i got close lightning hit it and more skeleton horses appeared with skeletons riding them, what exactly happened?
I think you found a Skeleton trap. You'll find it documented around a third or halfway down this page: http://minecraft.gamepedia.com/Horse
Not sure if it'll work on EMC, but in my 1.10 single player world I was able to ride one of the skeleton horses, I think you just have to hit them once with your fist. Not sure if you can eggify them, but it's worth a shot.
I remember me and SkyDragonv8/StoneSky/Unoski have a discussion about it with Aikar about why it wasn't allowed. I hope it gets implemented once, but unless it changed recently, it's not possible to ride skeleton horses on EMC. It is in Vanilla, though.