Use JavaScript Standard Style

Introduce JavaScript Standard Style as project style rule,
and fixed all fail on backend code.

lib/migrations/20160607060246-support-revision.js

@@ -1,8 +1,6 @@
-'use strict';
-
 module.exports = {
   up: function (queryInterface, Sequelize) {
-    queryInterface.addColumn('Notes', 'savedAt', Sequelize.DATE);
+    queryInterface.addColumn('Notes', 'savedAt', Sequelize.DATE)
     queryInterface.createTable('Revisions', {
       id: {
         type: Sequelize.UUID,
@@ -15,13 +13,11 @@ module.exports = {
       length: Sequelize.INTEGER,
       createdAt: Sequelize.DATE,
       updatedAt: Sequelize.DATE
-    });
-    return;
+    })
   },
 
   down: function (queryInterface, Sequelize) {
-    queryInterface.dropTable('Revisions');
-    queryInterface.removeColumn('Notes', 'savedAt');
-    return;
+    queryInterface.dropTable('Revisions')
+    queryInterface.removeColumn('Notes', 'savedAt')
   }
-};
+}