Using system brew cleanup instead of deprecated brew cask cleanup

[ondrejfuhrer]

brew cask cleanup is deprecated now, will be disabled on 2018-09-30 and the base brew cleanup should be used.

Updated the --cleanup option to use brew cleanup system command.

[KarlZeo]

@buo Please fix.brew cask cleanup is deprecated and will be disabled on 2018-09-30! Must use brew cleanup instead.

[kallookoo]

Add more info: brew cleanup not deleted latest downloads of the cask update. brew cleanup output help:

brew cleanup [--prune=days] [--dry-run] [-s] [formula/cask ...]:
    Remove stale lock files and outdated downloads for formulae and casks,
    and remove old versions of installed formulae. If arguments are specified,
    only do this for the specified formulae and casks.

    If --prune=days is specified, remove all cache files older than days.

    If --dry-run or -n is passed, show what would be removed, but do not
    actually remove anything.

    If -s is passed, scrub the cache, including downloads for even the latest
    versions. Note downloads for any installed formula or cask will still not
    be deleted. If you want to delete those too: rm -rf $(brew --cache)

Three possible options is:

• for loop file inside cache and execute brew cleanup cask_filename
• execute brew cleanup --prune=0 delete cache and logs
• rm -rf $(brew --cache)

[ondrejfuhrer]

Thanks @kallookoo for that update. I think for now this version introduced in the MR is fine, at least some cleanup will work. I'm not sure if we really want to do something more then what brew itself is doing, which could lead into some inconsistencies and future issues.

[ondrejfuhrer]

Closed in favour of #110 since it was causing problems there as well.