Renamed ngTableParams to NgTableParams

When using the ngTable into our application we've encountered a jshint error because the ngTableParams is a method that is starting with a lower case instead of uppercase letter.

This issue can be sorted out by activating newcap in jshint so you can ignore it. 
/* jshint newcap:true */

However, I've renamed the ngTableParams with NgTableParams so we could use jshint with default options and have no errors when placing ngTable inside our app.

This fix is for issue https://github.com/esvit/ng-table/issues/359