README: Update perf results & add firefox, safari
README: Update perf results & add firefox, safari

feross/buffer,btd/buffer,feross/buffer,btd/buffer,LiuDeng/buffer,LinusU/buffer,kawanet/buffer,SAGV/buffer,loon3/buffer,LiuDeng/buffer,loon3/buffer,kawanet/buffer,nolanlawson/buffer,beni55/buffer,nolanlawson/buffer,beni55/buffer,SAGV/buffer,jessetane/buffer,LinusU/buffer,feross/buffer