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 .
Shouldn't! You could do something like

```
.comment:nth-child(2n) {
    // some even styles
}

.comment:nth-child(2n + 1) {
   // some odd styles
}
```

If you're using scss it's even more compact

```
.comment {
    // styles common to all comments
    &:nth-child(2n) {
        // even specific
    }

    &:nth-child(2n+1) {
         // odd specific
    }
}

```

Hopefully syntax isn't wrong but that's the idea.