Reworked some release machinery.

A Rubinius -v line looks like the following:

  rubinius 2.0.0n270 (2.1.0 bff14074 2013-09-27 JI) [x86_64-darwin13.0.0]

For releases, the version will be only X.Y.Z. For non-release builds, the
version will be X.Y.Z.nNNN. The commit hash (bff14074 above) and the date
are included in both.