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

* Add quotes ESLint rule

* Add jsx-quotes ESlint rule

* Sort ESLint rules

* 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

* 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

* refactor(components/status_list): Avoid quering scrollTop if not necessary

* refactor(components/dropdown_menu): Do not render items if not expanded

* refactor: Cherry-pick react-motion imports

* refactor(compose/privacy_dropdown): Do not render options if not open

* refactor(components/column_collapsable): Do not render children if collapsed

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

Closes tootsuite/mastodon#1349

This is my first PR and I’m only checking in the source JSX file.
Please let me know if it should be checked in after being built also.

* 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

* Reorder javascript English locale file

 * Reorder translation string in order of the locale key.

* Add javascript English locale missing language keys

 * Search all javascript language keys by command:
   `grep -REho '<FormattedMessage .*\/>' ./app/assets/javascripts/.`

 * Add all the missing language keys and their values to `en.jsx`.

* Add javascript English locale missing language keys (2)

* Find all `defineMessages` calls with this command:
  `grep -Rl 'defineMessages({.*' ./app/assets/javascripts/.`

* Open all these files. Find the language key (`id`) in these
  statements.

* Add all the missing language keys and their values to `en.jsx`.

* Remove javascript English locale obsoleted language keys

 * Find all language keys that no longer exists in the source code
  and remove them. The removed keys include:

    * "compose_form.private"
    * "compose_form.unlisted"
    * "getting_started.about_addressing"
    * "getting_started.about_shortcuts"
    * "notification.mention"
    * "search.account"
    * "search.hashtag"
    * "tabs_bar.mentions"
    * "tabs_bar.public"

* Javascript English locale file add note

 * Add notes to contributors about the English translation files.
   Hope that will make translation process smoother.

* Update javascript locale defaultValue in code

 * Update the defaultValue in code according to the relevant
   translation in English locale file.