Replace Laravel Facades with Statical library

I have been testing my [static proxy library](https://github.com/johnstevenson/statical) with a few frameworks (prior to publishing it on Packagist) and came across your excellent Slim Facades. It wired up very smoothly so I wondered if you would prefer to use it in place of your Laravel Facade implementation.

I am not trying to push my library, so feel free to bin it and close this PR. 
Thanks for your time.