add a template_wrapper partial

I was thinking about how to fix link colors for the dynamic post color, and I realized: rather than copying the `<section>` tag and metadata include to every template, why not pull those things up a level? Then I can manage the color code in one place.

* adjust `partial` helper to take an optional template
* pass template through to `template_wrapper`
* remove support for per-item classes, but automatically add `hreview` class if `action_type` is `review` (maintains netflix rating support)
* `template_wrapper` handles `section` tag, metadata, and sets per-item link color
* simplify templates
actually link to instagram photos
bitcoin, because why not