Added alexbilbie/Proton under Micro Frameworks

README.md

 * [Bullet PHP](http://bulletphp.com/) - A micro framework for building REST APIs.
 * [Fast Route](https://github.com/nikic/FastRoute) - A fast routing library.
 * [Pux](https://github.com/c9s/Pux) - Another fast routing library.
+* [Proton](https://github.com/alexbilbie/Proton) - StackPHP compatible micro framework
 
 ## Micro Framework Extras
 *Extras related to micro frameworks and routers.*