Voting

Allow for AJAXy voting on comments and articles. Resolves #14.


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I'd probably just change `valid_votable_type?` to have the plurals when I put it back in. Then, since I'll only be calling `params[:controller].singularize` once, I shouldn't need to worry about setting it as a var or creating a method (at least for performance considerations--readability might be a different issue with all of those chained method calls).