Commit updated setup.ml in oasis before tagging a release

[gildor478]

Right now, the tag is set independently of the generated tarball. The oasis project has actually a significant difference in its setup.ml, because we store the generated version in the VCS.

We should change the order to generation to have:

1. start a release
2. build oasis
3. use built oasis to generate setup.ml
4. generate the tarball
5. tag a release

The content of the release tarball will be closer to the content of the VCS for the release tag.

See #107 for someone affected by this discrepancy.