`package` command with `-path` specified should export tarball into that path

When you call zpm "package" with a path specified, e.g. `\foo\bar\`, it exports the code into `\foo\bar\` but creates the tarball at `\foo\bar.tgz\`. This is one directory level up from what is expected. The result should be `\foo\bar\-.tgz`. If such a file already exists, it should overwrite but provide a warning that overwriting has happened.

Note, this may break people's automation/workflows so is backwards incompatible.