Munki 2 support and some minor fixes

Support [Munki 2](http://managingosx.wordpress.com/2014/09/17/munki-2-released/)'s new features:
- Provide the package icon at the expected path
- Include the packages categories in the catalog
- 404 the client_resources ZIP file (for now)

Other:
- Extract the Content-disposition filename field for files pulled from a URL
- OS Versions array extended to 10.9.5 and 10.10
- Prevent an exception in version_tracker
- Fix XML compliance of HTML