Add help about how to remove an old h2o package if one exists.
Revert "Update R README to the new cran-style approach."

This reverts commit 393fb8bd062b6ae1bccd5489d7dd0628afe18db6.
Put back R stuff, but fixed the file name.
Put the source R package and the README back in the master zip file.
Do not include the 6 copies of the binary package.