v0.002100

v0.002100

       - Wrap upgrades, downgrades, and installs in a transaction, as a failure
         to add a version to the version table should cause a rollback
       - Allow user to specify version of schema to install
       - Added better sandboxing (stolen straight from Plack::Util) for coderefs
         to avoid accidental leakage
       - Sandboxing also makes $0 and thus FindBin et al work in perl scripts