Backports daefbd66a6

* 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

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

* Add semi to ESLint rules

* Add padded-blocks to ESLint rules

* Add comma-dangle to ESLint rules

* add config/webpack and storyboard

* add streaming/

* yarn test:lint -- --fix

Use ES Class Fields & Static Properties (currently stage 2) for improve class outlook.

Added babel-plugin-transform-class-properties as a Babel plugin.

* Replace browserify with webpack

* Add react-intl-translations-manager

* Do not minify in development, add offline-plugin for ServiceWorker background cache updates

* Adjust tests and dependencies

* Fix production deployments

* Fix tests

* More optimizations

* Improve travis cache for npm stuff

* Re-run travis

* Add back support for custom.scss as before

* Remove offline-plugin and babili

* Fix issue with Immutable.List().unshift(...values) not working as expected

* Make travis load schema instead of running all migrations in sequence

* Fix missing React import in WarningContainer. Optimize rendering performance by using ImmutablePureComponent instead of
React.PureComponent. ImmutablePureComponent uses Immutable.is() to compare props. Replace dynamic callback bindings in
<UI />

* Add react definitions to places that use JSX

* Add Procfile.dev for running rails, webpack and streaming API at the same time

* fix(classnames): Status icon style classnames

Take out inline css and put into classnames for the following components: account, avatar, icon button, status action bar, notification.

* fix(status): Move styles from inline to classes for statuses

Move styles to classnames in components.scss for the following components:

display name
media gallery
status
status content
video player

* fix(classnames): Add classnames to rest of components

Take out inline styles and apply them to classnames in the sass for the following components:

button
column back button
slim column back button
collapsable column
dropdown menu
loading indicator
status list

* fix(classnames): Remove all non-dynamic inline styles

Components affected:

autosuggested
permalink
action bar
header
character counter
compose form
emoji dropdown
privacy dropdown
reply indicator
upload form
account auth
followers
getting started
column settings
mutes
settings
reblogs
status checkbox
report
action bar
status
card
boost modal
media modal
video modal

* fix(permalink): Do not lose classname

* fix(tests): Add space back in display name

* fix(status__wrapper): Remove duplicate css name

Remove incorrect style attribute. Remove style attribute all together. Cursor defaults to "auto" when not specified as 'default'.

* fix(nl): do not lose translations

* feat(aria): Add aria-labels to underlabelled tab nav items

The drawer tabs which control primary navigation are only labelled by a title which is not available to many screenreaders. Add an aria-label attribute to each link to improve readability with screenreaders. Organize link attributes so link target is first followed by classname.
Issue #1349

* feat(aria): Replace abstract aria role of section with region

Abstract aria roles such as section should not be used in content. Use non-abstract 'region' aria role instead. That role expects an aria-labelledby attribute with an id. Pass an ID to the column header. Remove the aria-label attribute on the ColumnHeader because the same value is output in plaintext as its child.
Issue #1349

* fix(aria): Remove aria-controls attribute until solution is found

Columns do not have wrappers, so these icons can't point to a column wrapper which it controls. Instead these icons function as triggers to show or hide individual columns.
#1349

* fix(typo): Remove type of aria-labelledby instead of aria-label

* Remove deprecated features at React v15.5

- [x] React.PropTypes
- [x] react-addons-pure-render-mixin
- [x] react-addons-test-utils

* Uncommented out & Add browserify_rails options

* re-add react-addons-shallow

* Fix syntax error from resolve conflicts

* follow up 59a77923b3

* Hides superluous details on small screans.

* Addressed feedback from #2175.

* Add eslint-plugin-jsx-a11y.

* Fix npm script.

* Adjust npm scripts so test also runs lint.

* Fix existing lint errors.

* Don't break on a11y issues.

* Add role and tabIndex.

* Add vim and Mac files to .gitignore and .dockerignore.

* Handle htmlFor (partially), a that's actually a button.

* Fix missing tabIndex.

* Add cursor:pointer to load-more

* Revert change to load_more.

* Fixes based on review.

* Update yarn.lock.

* Don't try to install fsevents on Linux (hides warning noise).

Closes mastodon#1720