I adapt the code of Alex Bilbe for work with non deprecated mongoclient.
I don't test it all. But it's works for me.

PLEASE NOTE: Alex Bilbe (http://www.alexbilbie.com) has merged this fork of his original code back into his own. http://bitbucket.org/alexbilbie/codeigniter-mongo-library/wiki/Home

====================================================================================================
	GETTING STARTED
====================================================================================================

1.  Add the mongo_db.php config file to your ./system/application/config directory and make the 
		appropriate changes to connect to your database

2.	Copy the Mongo_db.php library file to your ./system/application/libraries directory
3.	(optional) Add the library to your autoload.php file if you plan to frequently reference the library