Updated README for 1.2-beta1. Added BETA warning.
Updated README for 1.2-beta1. Added BETA warning.

CatoTH/OpenSlides,CatoTH/OpenSlides,boehlke/OpenSlides,ostcar/OpenSlides,FinnStutzenstein/OpenSlides,jwinzer/OpenSlides,tsiegleauq/OpenSlides,jwinzer/OpenSlides,CatoTH/OpenSlides,rolandgeider/OpenSlides,normanjaeckel/OpenSlides,ostcar/OpenSlides,jwinzer/OpenSlides,FinnStutzenstein/OpenSlides,boehlke/OpenSlides,boehlke/OpenSlides,jwinzer/OpenSlides,normanjaeckel/OpenSlides,emanuelschuetze/OpenSlides,jwinzer/OpenSlides,boehlke/OpenSlides,tsiegleauq/OpenSlides,FinnStutzenstein/OpenSlides,emanuelschuetze/OpenSlides,normanjaeckel/OpenSlides,emanuelschuetze/OpenSlides,normanjaeckel/OpenSlides,FinnStutzenstein/OpenSlides,OpenSlides/OpenSlides,tsiegleauq/OpenSlides,rolandgeider/OpenSlides,OpenSlides/OpenSlides,ostcar/OpenSlides,rolandgeider/OpenSlides,CatoTH/OpenSlides,emanuelschuetze/OpenSlides