A new rake task emojis:generate downloads a full list of valid
unicode sequences from unicode.org and checks it against existing
Twemoji files, finally generating a map from each sequence to the
existing file (e.g. when there's multiple ways an emoji can be
expressed). The map is dumped into app/javascript/mastodon/emoji_map.json

That file is loaded by emojione_light.js (now a misnomer) which
decorates it further with shortcodes taken from emoji-mart's index.

We added horizontal layout to preview card for wide image. However, max height of the thumbnail is still limited to 120px and it makes nearly square images to too small for that layout.

This PR increases max height as well as max width.

* Thread toot notification mails by conversation

* Make codeclimate happy and avoid potential mis-threading

* In detail status view, display attachment uncropped if there's only one

* Make media spoiler the size of the media it hides, enable on static

630px = Drawer + 1 Column

- Moved building the secondary btn text into the if to avoid trying to translate 'none' visibility

Add secondary toot button + other toot button enhancements. 
Squashing so it's easy to revert if needed.

* Fix numbers in accounts columns

* Support edge compact-header

* Add emoji autosuggest

Some credit goes to glitch-soc/mastodon#149

* Remove server-side shortcode->unicode conversion

* Insert shortcode when suggestion is custom emoji

* Remove remnant of server-side emojis

* Update style of autosuggestions

* Fix wrong emoji filenames generated in autosuggest item

* Do not lazy load emoji picker, as that no longer works

* Fix custom emoji autosuggest

* Fix multiple "Custom" categories getting added to emoji index, only add once

* Switch from EmojiOne to Twemoji, different emoji picker

* Make emoji-mart use a local spritesheet

* Fix emojify test

* yarn manage:translations

* Fix the migration error when deprecated_preview_cards has deleted

* Re-run Travis CI

This addresses a comment during review:
https://github.com/tootsuite/mastodon/pull/4801#discussion_r139337452

This means we'll need to make sure that all _id columns going forward
are bigints, but that should happen automatically in most cases.

* Make dropdowns render into portal, expand animation

* Improve actions modal style

Improvements to status headers and content

Emoji and Hashtag autocomplete

When colon appears end of line, skiped all character containing unicode emojis. Fixed.
https://github.com/tootsuite/mastodon/pull/5016#issuecomment-331012008