Add in support for ac-php / a company backend

I'm an avid user of https://github.com/xcwen/ac-php, specifically company-php. I think it'd be a great idea to include this package into php-suite since it has code completion, documentation popups (via company-quickhelp), and jumping back and forth from function definitions.

I believe that https://github.com/emacs-php/phpactor.el does all of the above, so I understand if ac-php is not included.