Validate that output buffer works as expected each template on render and correctly identifies AMP components

[postphotos]

AC1: The rendered PHP output from each page template (index.php, single.php, archive.php, etc.) should be output buffered to control what specific output is sent in the response from the templates.

• Because PHP parsing is piecemealed and complex, theme markup rendering can become more efficient if rendered using output buffering.
• As a result of working shortcodes and page templates, and components (sidebar.php, comments.php)

AC2: The buffered output should be modified to remove elements and attributes that are invalid AMP.

• <script> tags, for example, should not renderable from widget or content areas on the front end.

AC3: Each output buffer logic should play nicely with the the AMP plugin to filter standard HTML markup into valid, AMP-compatible markup. Standard HTML output by the theme should get converted over to AMP equivalents, such as using action-xhr attribute for POST forms instead of action attributes.

AC4: As a result of this template output buffering, AMP pages should not have visual or functional regression compared to their HTML versions in support of rendering AMP canonical pages.

[kopepasah]

@postphotos I believe this issue should be added to the plugin, as there is nothing to do theme wise to verify this markup, all the parsing happens in the plugin.