`Zip.sort_entries` working for zip output

The display of entries (from the `EntrySet.entries`) method works as advertised, but the actual entries in the zip that's created isn't sorted right now because `each` isn't aware of the `sort_entries` setting.

This PR changes that.

Note that this relies on the fact that RubyZip now has 1.9.2 (ie. ordered Hashes) as a requirement.