Replace db factory and do not promisify the commands

lib/db.js

@@ -1,7 +1,4 @@
 const logger = require('./logger').db;
-const redisCommands = require('redis-commands');
-require('util.promisify/shim')(); // NOTE: shim for native node 8.0 uril.promisify
-const util = require('util');
 let db;
 
 module.exports = function () {
@@ -15,19 +12,9 @@ module.exports = function () {
   // designed for demo and test scenarious to avoid having real Redis instance
   const emulate = process.argv[2] === 'emulate' || redisOptions.emulate;
 
-  const redis = require(emulate ? 'fakeredis' : 'redis');
-  promisify(redis.RedisClient.prototype, redisCommands.list);
-  promisify(redis.Multi.prototype, ['exec', 'execAtomic']);
+  const Redis = require(emulate ? 'ioredis-mock' : 'ioredis');
 
-  function promisify (obj, methods) {
-    methods.forEach((method) => {
-      if (obj[method]) {
-        obj[method + 'Async'] = util.promisify(obj[method]);
-      }
-    });
-  }
-
-  db = redis.createClient(redisOptions);
+  db = new Redis(redisOptions);
 
   db.on('ready', function () {
     logger.debug('Redis is ready');