Commenting

Add commenting feature to Hacker News clone. Also formalizes the relationship between `Articles` and `Users` and includes stylistic changes and some basic refactoring. Resolves #12 .
sorry for the delay, in your first link (articles/index), that `article` is coming from the `@articles.each` loop. In the second (articles/show) it doesn't really make sense that this helper is used for that. I would assume the `@article` instance variable you're setting in your `show` method in this controller would be used for that view.

The main red flag I see here is that `current_user.articles.build(article_params)` looks like some code that should only be used in the `create` action.