* Custom emoji

- In OStatus: `<link rel="emoji" name="coolcat" href="http://..." />`
- In ActivityPub: `{ type: "Emoji", name: ":coolcat:", href: "http://..." }`
- In REST API: Status object includes `emojis` array (`shortcode`, `url`)
- Domain blocks with reject media stop emojis
- Emoji file up to 50KB
- Web UI handles custom emojis
- Static pages render custom emojis as `<img />` tags

Side effects:

- Undo #4500 optimization, as I needed to modify it to restore
  shortcode handling in emojify()
- Formatter#plaintext should now make sure stripped out line-breaks
  and paragraphs are replaced with newlines

* Fix emoji at the start not being converted

* So Spanish. Much changes. Wow.

* Some little fixes

* Updated es.yml, and fixed some ortographical errors

* Some little changes to simple_form.es.yml

* Yeah, so much translations

* Spanish e-mail messages

* Remove unused message

Limiting allowed characters in the last character of the URL is came from twitter-text, but underscore is allowed on there, and Mastodon before #4941.

Since reblogs are serialized as Announce activity, its published property can be used for the creation time of reblog.

It is faster.

* Bump ruby version to 2.4.2

https://www.ruby-lang.org/en/news/2017/09/14/ruby-2-4-2-released/

Gemfile.lock is also updated.

TODO
- [ ] Update Dockerfile with Alpine release of ruby-2.4.2

* Revert jwt version

It seems that jwt 2.0.0 fails in some environment.
ref. https://github.com/zaru/webpush/issues/42

* Bump Ruby version on docker image

* Oauth code in a input form and add description

* New authcode description

We had returned `nil` for that case, but this raises an error instead, as a wrong usage of the method.
This method is currently only used in ActivitySerializer.

SubscriptionsScheduler in particular causes high load across the
entire fediverse at 5 AM UTC every day. Randomizing cron schedules
and/or adding a random delay is considered best practice to avoid
this issue.

* Fix an error when actor json couldn't be fetched in ResolveRemoteAccountService

* Add specs

* zh-*: transition from "like" back to "fav"

This commit reverts the translation for the yellow-star "fav" button
back to "fav" in Chinese. Some ambuiguity between "like" and "fav" is
deliberately used in zh-TW/HK by using the existing phrase "最爱"
(favorite (adj.), lit. love-most) instead of "收藏" (favourite (v.),
"collect") in some instances.

Fixes #3511.

* zh-*: apply suggestions for PR #4557

* zh-cn: de-monetize ya account

In Chinese two separate characters, 账 and 帐, can be used to spell the
word for account (账/帐户). However, the one with a 贝 on the left is
evolved from the latter specifically for monetary purposes. Since
people usually can't figure out which one to use, it might be a good
idea to use the original not-so-money one.

* zh-*: complete jsx translation

* Adjust landing pages 2

Fix styles of terms page
Remove action buttons from timeline in about page
Adjust styles of short description
Adjust form inputs
Set autocomplete off for username and email box in registration form. Remove line breakings.

* Revert removing action buttons

Reply distribution is proceed by Sidekiq, so replied status may be deleted before this.

`Status#reply?` may returns true even if the thread is missing.
e.g. the replied status was deleted or couldn't be fetched.

Then it raises NoMethodError on various AP json serialization.

This issue won't happen on Atom serialization because it checks thread
existence using `StreamEntry#threaded?` instead.

* When accessing uncached media attachment, redownload it

* Prevent re-download of rejected media

* Fix behavior while the button is invisible
e.g. pointer cursor, couldn't open contextmenu
* Avoid rendering the button to remove blank space if no more items are available or no items are rendered

* devise.pt-BR.yml now fully translated

* pt-BR.json now fully translated

* pt-BR.yml partially translated; 46 lines left

* pt-BR.yml now fully translated

* simple_form.pt-BR.yml fully translated

* doorkeeper.pt-BR.yml now fully translated

* E-mail instructions on app/views/user_mailer added and fully translated

* PT-BR translation for #4871

* Deleted an unwanted caracter on pt-BR.yml

* Fixing typos on pt-BR.yml

* Added translation for Pinned toots tab on pt-BR.json

* Added missing translation for navigation_bar.pins

* Fixed spelling on pt-BR.yml

* Update pt-BR.json

* Add scheduled worker to purge old user IPs

* Use ruby 1.9 hash syntax

* Fix race condition when receiving an ActivityPub Create multiple times

* Use a RedisLock to avoid concurrent processing of a same Create activity

* Revert "Enable UniqueRetryJobMiddleware even when called from sidekiq worker (#4836)"

This reverts commit 6859d4c0.

* Revert "Do not execute the job with the same arguments as the retry job (#4814)"

This reverts commit be7ffa2d.