zip_kalite should exclude subtitles and subtitle data

Issue:
* @dylanjbarth checked in some fantastic subtitles changes.  Zipping scripts were not updated to exclude those files in the packaging.
* This also required partially addressing #595, as one of the excluded files is currently a main dependency, which breaks stuff when removed from the zip packaging.

Changes:
* The right fix would be to use the .gitignore file.  For now, just duplicate that logic into the zip_kalite management command.
* Also ensure that the destination directory exists.

Testing:
* Ran the script, made sure it excluded the subtitles files.