Replace sprockets/browserify with Webpack (#2617)

* 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

docker-compose.yml

@@ -15,10 +15,14 @@ services:
 #    volumes:
 #      - ./redis:/data
 
-  web:
-    restart: always
+  app:
     build: .
     image: gargron/mastodon
+
+  web:
+    extends:
+      service: app
+    restart: always
     env_file: .env.production
     command: bundle exec rails s -p 3000 -b '0.0.0.0'
     ports:
@@ -28,12 +32,13 @@ services:
       - redis
     volumes:
       - ./public/assets:/mastodon/public/assets
+      - ./public/packs:/mastodon/public/packs
       - ./public/system:/mastodon/public/system
 
   streaming:
+    extends:
+      service: app
     restart: always
-    build: .
-    image: gargron/mastodon
     env_file: .env.production
     command: npm run start
     ports:
@@ -43,9 +48,9 @@ services:
       - redis
 
   sidekiq:
+    extends:
+      service: app
     restart: always
-    build: .
-    image: gargron/mastodon
     env_file: .env.production
     command: bundle exec sidekiq -q default -q mailers -q pull -q push
     depends_on: