Figure out a way to not have 3 nested foreach loops

[kkoppenhaver]

Current status: O(scary)

[kkoppenhaver]

Per @rinatkhaziev, use the same parser that Facebook Instant Articles plugin uses to transform their HTML.

[kkoppenhaver]

https://github.com/facebook/facebook-instant-articles-sdk-php

Transformer: An engine for transforming any markup into an Instant Article structure in the DSL. The engine runs a set of rules on the markup that will specify the selection and transformation of elements output by the CMS into their Instant Articles counterparts. The transformer ships with a base set of rules for common elements (such as a basic paragraph or an image) that can be extended and customized by developers utilizing the SDK.

So instead of transforming posts into IA markup, we'd use our own custom transform rules instead of handcoding them like we're doing now.