Update Mounts.css

Updated with periods and ethereal lion position.

Can't update the sprite sheet just this moment in my repo but it has been made. See attached for new mount sprite sheet.
![Mount-SpriteSheet](https://f.cloud.github.com/assets/2374703/304001/e79a0d96-9632-11e2-9254-ac40b3e1ecb3.png)

Can either take this pull request and replace image yourself or wait for another pull request tonight from me which includes image file.

Untested!