I have recently installed Magento2. CSS and JS not loading after installing Magento 2. I have used composer to install. This magento 2 files I have taken by a checkout from a live website. Also the php magento setup:static-content:deploy command is not working. Running this command gives the following error:

PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php5/20131226/mongo.so' - /usr/lib/php5/20131226/mongo.so: cannot open shared object file: No such file or directory in Unknown on line 0 Could not open input file: magento