code: function( userId, id ) {
  
  		return this.memory.joinRoom( userId, id )
  		.then( function( id ) {
  
  			if( rooms[ id ] === undefined ) {
  
  				rooms[ id ] = room( this.memory, id );	
  			}
  			
  			return promise.resolve( rooms[ id ] );
  		}.bind( this ));
  	}
docs: Join a room
  
  @param  {String} userId id of the user whose entering a room
  @param {String} id id for the room you'd like to enter
  @return {Promise} This promise will resolve by sending a room instance if the room does not exist it will fail