Automatically add ugoira tag to ugoira posts.

Note that this only adds the ugoira tag to .zip posts. It does not
remove the ugoira tag for posts converted from ugoira, but that aren't
true ugoira.
Ensure JSON API returns boolean for Post#has_large.

Currently the JSON API returns null for false and 0 for true for this
attribute. Cast it to a boolean instead.
Include ugoira frames in post data attributes.
Include ugoira data in post JSON API.
Merge pull request #2287 from evazion/fix-has-large

Ensure JSON API returns boolean for Post#has_large.
Merge pull request #2286 from evazion/fix-ugoira-api

Include ugoira data in data attributes and JSON API
Merge pull request #2282 from evazion/feat-autotag-ugoira

Automatically add ugoira tag to ugoira posts.