Merge pull request #1150 from mrlynn/master

Add MongoDB PHP Driver

README.md

 ### NoSQL
 *Libraries for working with "NoSQL" backends.*
 
+* [MongoDB](https://github.com/mongodb/mongo-php-driver) - MongoDB PHP Driver.
 * [PHPMongo](https://github.com/sokil/php-mongo) - A MongoDB ORM.
 * [Predis](https://github.com/predis/predis) - A feature-complete Redis library.