Voting

Allow for AJAXy voting on comments and articles. Resolves #14.


![](http://zippy.gfycat.com/ImpracticalPastCardinal.gif)
The original looked like:
```
def votable
  @votable = begin
    params.each do |name, value|
      if name =~ /(.+)_id$/ && valid_votable_type?($1)
        return $1.classify.constantize.find(value)
      end
    end
    nil
  end
end
```
This depended on there being either a `params[:article_id]` or `params[:comment_id]`. After refactoring the routes, there wasn't an `article_id` or `comment_id` parameter. Instead, there are `controller` and `id` params. 

In typing this response, I realize that I can change the previous code to look like `if name =~ /(.+)s$/ && valid_votable_type?($1)` and `return $1.classify.constantize.find(params[:id])`, which would let me keep it more similar to the original pattern. Would that be worth it?