update vignette to use xyplot2
merge with collab

* collab:
  update vignette to use xyplot2

git-svn-id: https://hedgehog.fhcrc.org/bioconductor/trunk/madman/Rpacks/VanillaICE@73057 bc3139a8-67e5-0310-9ffc-ced21a209358