compare bin and lib versions, and error out on mismatch

compare bin and lib versions, and error out on mismatch

This should help the occasional bug reports that happen because someone
runs bin/sup from development, but somehow picks up libraries from a
pre-installed gem.

To make "rake gem" still function when working from a checkout, we fake
a version number of 999. (Gem versions must be dotted numerics.)

It won't detect version mismatches against gems that have been installed
via "rake gem" from a checkout, but that is typically a less common
issue.