* Upgrade to React 16.0.0

* Disable some uncritical tests while chai-enzyme remains incompatible

* fix(compose): Add aria-label for the navigation links

* fix(search): Add input label

* fix(navigation_bar): Link description

* fix(autosuggest_textarea): Add input label

* fix(compose_form): Add input label

* fix(upload_button): Add input label

* fix(account/header): Add link content

* fix(column_header): Use h1 tag

* fix(column_header): Labels move buttons moving column

* fix(settings_text): Add label to input

* fix(column_header): Remove role from h1

* fix(modal_root): Use role=dialog

* fix(modal_root): Focus restauration

* fix(modal_root): Apply inert to sibligs

* fix(column_header): Add role=button

* chore(eslint): Disable jsx-a11y/label-has-for

* fix(column_header): Invalid ARIA role

* fix(column): Remove hidden nodes from the DOM

* refactor(column_link): Remove unused property hideOnMobile

* fix(column_header): Use aria-pressed

* fix(column_header): Make collapsed content not focusable, add focusable property

* fix(column_loading): Make header non-focusable

* fix(column_settings): Use role to group the toggles

* fix(compose): Use nav and remove redundant aria-label

* fix(tabs_tab): Use nav and add aria-label

* fix(app): Add aria-label for settings toggle button

* chore: Run yarn manage:translations

* feat: Replace react-swipeable with react-swipeable-views

* fix: iOS 9

* Remove unused column_collapsable.js
* Remove old styles
* Extract `> div`  style to independent class

ref https://tc39.github.io/proposal-decorators/

* chore(yarn): Remove react-router

* chore(yarn): Remove react-router-scroll

* chore(yarn): Remove history

* chore(yarn): Add react-router-dom

* chore: Remove usages of react-router-scroll

* refactor: Upgrade to react-router-web

* refactor: Use fork of react-router-scroll

This reverts commit 2ddea9a6c8.

* fix: Issues mentions in the PR feedback

* Unread indicator was invisible behind column header, adjusted

* Unread indicator now a CSS pseudo-element

* Adjust flex

* Allow mounting arbitrary columns

* Refactor column headers, allow pinning/unpinning and moving columns around

* Collapse animation

* Re-introduce scroll to top

* Save column settings properly, do not display pin options in
single-column view, do not display collapse icon if there is
nothing to collapse

* Fix one instance of public timeline being closed closing the stream
Fix back buttons inconsistently sending you back to / even if history exists

* Getting started displays links to columns that are not mounted