Voting

Allow for AJAXy voting on comments and articles. Resolves #14.


![](http://zippy.gfycat.com/ImpracticalPastCardinal.gif)
Wow, I like this a lot. Is `render status: :unprocessable_entity` probably the right way to go for errors? I can't think of a different reason off the top of my head that would cause the `else` to be called, but it also seems a little odd to hardcode the 422.