updated readme with 2.0 announcement
updated readme with 2.0 announcement

cookchristopher/BackstopJS,garris/BackstopJS,cookchristopher/BackstopJS,garris/BackstopJS,klausbayrhammer/BackstopJS,mirzazeyrek/BackstopJS,mirzazeyrek/BackstopJS,garris/BackstopJS,klausbayrhammer/BackstopJS