- abstracts out common logic, much code removed
- fixes one bug/inconsistency: some artifacts failed to
"return false" when the target exists in "preflight_checks".
- one trivial functional change: artifact type and quotation marks
added in all user feedback (quotes needed b/c of pathnames
containing spaces)
- this allows us to support casks for things like "dmg in zip" "zip in
tar", etc, etc
- a nested container can be any format that homebrew-cask supports
- the existing container support is now referred to as a Cask's
"primary container"
- use the `nested_container` artifact type to indicate the relative
path to a nested container that you wanted extracted
- multiple layers of nesting should work with multiple nested_container
directives (though this is untested as yet)
- add SpeedDownload as the first cask to use this feature; refs #602
Roland Walker