- Add postcss with autoprefixer and cleancss

Also, remove the Promise polyfill. We don't support browsers which don't support promises.

- hot reloading
- split config into dev and prod

- Removes the need for generating and keeping json files

* Order by category
* Set odering pre category (instead of just showing them alphabetically)

* Add emoji tooltip
* Make categories configurable and add smileys category
* Rearrange emoji categories and style
& Show all emojis together

This fix forces Converse.js to respect auto_join_rooms and allow auto join room to occur with server-side generated random room names as required for XEP 0142 - workgroup queues

Currently translated at 100.0% (393 of 393 strings)

Translation: Converse.js/Translations
Translate-URL: https://hosted.weblate.org/projects/conversejs/translations/af/

Currently translated at 100.0% (393 of 393 strings)

Translation: Converse.js/Translations
Translate-URL: https://hosted.weblate.org/projects/conversejs/translations/fr/

Currently translated at 84.0% (330 of 393 strings)

Translation: Converse.js/Translations
Translate-URL: https://hosted.weblate.org/projects/conversejs/translations/ar/

Currently translated at 100.0% (393 of 393 strings)

Translation: Converse.js/Translations
Translate-URL: https://hosted.weblate.org/projects/conversejs/translations/de/

Also:

* converted two docstrings into JSDoc format
* Don't use `_.isNull`

can cause messages to not appear.

* Check against null not Element.
* Avoid iterating over non-Element nodes

Lately we've been fetching messages only after entering the MUC, so that
we already have occupants to attach to them (due to `fetchMembers` being
called before) and thereby avoid rerenders.

I've now moved message fetching into the `initialize` method and added
missing event handlers for attaching/removing the occupant from a
message as it comes online or goes offline.

We still avoid (some) rerenders because we fetch and wait for cached
occupants before fetching cached messages and we wait for `fetchMembers`
before triggering `enteredNewRoom` which causes MAM messages to be
fetched.

Also fix scrolling bug

We want to fetch messages from cache only once. For one-on-one chats
this is the case because messages are fetched only in the `initialize`
method.

This used to be the case for MUCs as well, until we added the option
`clear_messages_on_reconnection`.

Now we only fetch messages after the user has entered the MUC.