MINOR: Reformatted readme into markdown (from r90301)
MINOR: Reformatted readme into markdown (from r90301)

mandrew/silverstripe-subsites,wernerkrauss/silverstripe-subsites,wernerkrauss/silverstripe-subsites,danaenz/silverstripe-subsites,mikenz/silverstripe-simplesubsites,petpack/silverstripe-subsites,dnadesign/silverstripe-subsites,danaenz/silverstripe-subsites,petpack/silverstripe-subsites,mikenz/silverstripe-simplesubsites,silverstripe/silverstripe-subsites,dnadesign/silverstripe-subsites,mandrew/silverstripe-subsites,silverstripe/silverstripe-subsites