document change in default BioC version
tweaks to layout and wording.


git-svn-id: https://svn.r-project.org/R/trunk@66776 00db46b3-68df-0310-9c12-caf00c1e9a41
need to move up loading the namespace

git-svn-id: https://svn.r-project.org/R/trunk@66782 00db46b3-68df-0310-9c12-caf00c1e9a41