Utility function for making sure a package is available with a particular version or newer.
checkForPackageWithVersion(pkg, vers)If the package with the required version or higher is available, TRUE is returned
invisibly. Otherwise FALSE is returned.
Character. The name of the package to check.
Character. The minimum acceptable version of the package. Will only be checked to the major.minor level.
Bryan A. Hanson (DePauw University).