Tar.gz and Zip downloads are different: the tarball should have the same content as the zip

@kimchy There is no reason IMHO for these to be different, which is quite surprising.

The .zip has extra files for Windows-only:
```bin/elasticsearch.bat
bin/plugin.bat
lib/sigar/sigar-amd64-winnt.dll
lib/sigar/sigar-x86-winnt.dll```

This means that the tar.gz distro CANNOT be used on Windows in practice.

The pull request fixes the file sets, though there is may be a simpler way to do this