Fix migration script of revision lacks of definition of primary key

lib/migrations/20160607060246-support-revision.js

@@ -4,7 +4,10 @@ module.exports = {
   up: function (queryInterface, Sequelize) {
     queryInterface.addColumn('Notes', 'savedAt', Sequelize.DATE);
     queryInterface.createTable('Revisions', {
-      id: Sequelize.UUID,
+      id: {
+        type: Sequelize.UUID,
+        primaryKey: true
+      },
       noteId: Sequelize.UUID,
       patch: Sequelize.TEXT,
       lastContent: Sequelize.TEXT,