Convert comments to React.js

This is more so @divad12 can take a look, I'm curious if there are things you would have done differently. (Though anyone feel free to leave comments). Not really too concerned about whether this ever gets merged, though I do think that the React version is much cleaner than the equivalent Backbone code. Would definitely check out converting other parts of the code, if it makes it cleaner/more readable and no one's overly opposed.