* Fix #3910 - Require OTP authentication to disable 2FA. Also, remove ability
to generate new OTP backup codes *after* initial backup codes were handed
out during activation

* Restore recovery code re-generation

* Improve display of some 2FA elements

* Add form for account deletion

* If avatar or header are gone from source, remove them

* Add option to have SuspendAccountService remove user record, add tests

* Exclude suspended accounts from search

* Add explit admin actions to (re)subscribe/unsubscribe remote accounts
and re-download avatar/header

* Improve how admin NSFW toggle looks

- Updates scss variables file to use better-named variables for black/white/etc
- Arranges the "mastodon classic" colors into variables
- Remove all references to `$color-*` naming, replacing with new

This does not in itself introduce "theme" support, but:

- It would probably be easier to start working on theme support after this
  change and others
- Even without the goal of themes, these changes make it more clear how the
  colors are being used.

There is almost definitely some edge case in here where I've guessed the
intent/context of some color usage incorrectly, but it still seems like a net
improvement.

* add scss_lint to Gemfile

* add .scss-lint.yml

* fix warnings of scss-lint

* chmod -x styles/variables.scss

* Enable CodeClimate SCSS Lint checks

* 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

* enable to scroll the setting's page sidebar

add scroll:auto and use margin instead of padding for the bottom

* Update admin.scss

* Update admin.scss

* Update admin.scss

* Remove overflow because it blocks scrolling on mobile safari.

* Add “-webkit-overflow-scrolling: touch;” to enable smooth scroll on mobile safari and other webkit browsers.

* Use radio buttons in user setting page.

Because select tags with long text are not fit in the width of mobile devices.

* Add flex property to fit labels to devise width.

* Change font size of select.

It causes auto zooming on mobile safari.