Voting

Allow for AJAXy voting on comments and articles. Resolves #14.


![](http://zippy.gfycat.com/ImpracticalPastCardinal.gif)
Now that I'm thinking about it, I'm not actually sure why I did this. Maybe I originally had `if @vote ...` rather than `if vote ...` in my `upvote` and `downvote` methods? Either way, I'll change it.