`drom` should store its version in `.drom` to prevent rollbacks with older versions

[lefessan]

If a user calls drom project with an older version of drom, an old skeleton might be used, and some updates done by a previous user may be lost. To prevent this scenario, drom should store its version in .drom when updating the files, and check before updating them again that it has an at-least-same-version, or fail.