Fixes #1348

Tried to get the unread messages indicator to line up properly with the
text and icons in a room list item.

Also tried to reuse styles where appropriate, specifically
`.list-container` and `.list-toggle`.

We distinguish between UniView and MultiView instances.

UniView means that only one chat is visible, even though there might be multiple ongoing chats.
MultiView means that multiple chats may be visible simultaneously.

by not flushing stanzas when sending out an <inactive> CSI.

When reloading the page, the stanzas are resent (because we never had
time to receive acks) which causes problems on Prosody (and likely also
causes the Ejabberd "other-request" errors).

Put the historical background info into a ``note`` and add short
explanations of the 4 different view modes

Otherwise they get cut off sometimes

https://blog.travis-ci.com/2018-11-19-required-linux-infrastructure-migration

`sudo: false` is getting deprecated and support for it will soon be
removed entirely. They seem to be moving to using VMs entirely for their
service.

Converse doesn't seem to be using Travis' features extensively so I
don't think anything would break, but this clause will become useless in
less than a month, (quite a tight timeline).
Signed-off-by: Maxime “pep” Buquet <pep@bouah.net>

This reverts commit 7af73c34.

Doesn't look like the right approach for adding support for XEP-0156.
Work on that will continue in a branch in the meantime.

Causes "Mixed Content" TLS errors