code: function RedisStore(port, host, options) {
  	port = port || 6379;
  	host = host || '127.0.0.1';
  	this._options = options || {};
  	this._options.redisstore = this._options.redisstore || {};
  	if(this._options.redisstore.database && !isNumber(this._options.redisstore.database)) {
  		throw new Error('database has to be a number (if provided at all)');
  	} else if(this._options.redisstore.database) {
  		this._database = this._options.redisstore.database;
  	} else {
  		this._database = 0;
  	}
  
  	this._tokenKey = this._options.redisstore.tokenkey || 'pwdless:';
  	delete this._options.redisstore;
  
  	this._client = redis.createClient(port, host, this._options);
  }
docs: Constructor of RedisStore
  @param {Number} [port] Port of the Redis server (default: 6379)
  @param {String} [host] Host, e.g. 127.0.0.1 (default: 127.0.0.1)
  @param {Object} [options] Combines both the options for the Redis client as well
  as the options for RedisStore. For the Redis options please refer back to
  the documentation: https://github.com/NodeRedis/node_redis. RedisStore accepts
  the following options: (1) { redisstore: { database: Number }} number of the
  Redis database to use (default: 0), (2) { redisstore: { tokenkey: String }} the
  prefix used for the RedisStore entries in the database (default: 'pwdless:')
  @constructor