Added stub support for TinderboxScraper (#180)

This PR addresses issue #180

I added support for stub installers on a windows platform.

The current latest tinderbox folder for windows does not have a stub installer. At the time of writing this a suitable test for functionality would be

`mozdownload -t tinderbox -p win32 --date=1382263322 --stub`

This will however change after awhile.