DSL convert last of test suite to `pkg` stanza

instead of `install`
doc nits re: caveats.  Broken anchor link.
update hashcat.rb to use depends_on :formula

This is the only Cask with `depends_on_formula` in the main repo.
doc: highlight `:pkgutil`

As the most-important `uninstall` directive
metadata directory support

- incidentally adds defensive driving against null version
  in method `destination_path`
Update Brackets to 0.43
Upgrade packer to 0.7.1
Merge pull request #6147 from whiteley/packer

Upgrade packer to 0.7.1
updated unity3d (4.5.4)
Merge pull request #6148 from vitorgalvao/update-unity3d

updated unity3d (4.5.4)
Renamed unity3d to unity
CONTRIBUTING.md: Adding unversioned Cask info

The docs seemed to suggest that if versioned downloads were available,
to prefer them over unversioned ones. Since that's incorrect presently,
I attempted to correct that (see #6126 for more details).
replaced vagrant with unity in examples referencing the pkg
Merge pull request #6145 from treyharris/versioning-docfix

CONTRIBUTING.md: Adding unversioned Cask info
Changed Firefox to Firefox.app in CONTRIBUTING, for consistency with other examples.
Merge pull request #6150 from vitorgalvao/change-vagrant-examples

replaced vagrant with unity in examples referencing the pkg
Merge pull request #6117 from rolandwalker/metadata_directories

Metadata directory support
Merge pull request #6137 from rolandwalker/dsl_pkg_test_suite

DSL convert last of test suite to `pkg` stanza
Merge pull request #6139 from rolandwalker/doc_nit_anchor

doc nits re: caveats.  Broken anchor link.
Merge pull request #6140 from rolandwalker/hashcat_depends_on

update hashcat.rb to use depends_on :formula