Add a mobile detect library

Mobile_Detect is a lightweight PHP class for detecting mobile devices (including tablets). It uses the User-Agent string combined with specific HTTP headers to detect the mobile environment.

README.md

@@ -641,6 +641,7 @@ Libraries to help manage database schemas and migrations.
 * [PHP-GPIO](https://github.com/ronanguilloux/php-gpio) - A library for playing with the Raspberry PI's GPIO pins.
 * [print_o](https://github.com/koriym/print_o) - An object graph visualizer.
 * [Alias](https://github.com/fuelphp/alias) - A class aliasing library.
+* [Mobile-Detect](https://github.com/serbanghita/Mobile-Detect) - A lightweight PHP class for detecting mobile devices (including tablets).
 
 # Software
 *Software for creating a development environment.*