Add fading in/out of upvote/downvote buttons

I saw your issue while using http://tevko.github.io/practice/github.html and added the fading for #30 for you.  Also just a small piece of advice you should be doing `.mim` for your css selectors more instead of `div.mim`.  If you need to qualify like that you should be adding more classes to make your selectors cleaner.  I like the site good luck with it!