Voting

Allow for AJAXy voting on comments and articles. Resolves #14.


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The conditional should [short-circuit evaluate](http://en.wikipedia.org/wiki/Short-circuit_evaluation), meaning that if `vote` were `nil`, then it wouldn't evaluate the following statements.  With that said, I support wrapping parens around the `||` clause to group them together and make it a bit more clear to the reader.