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
Renamed unity3d to unity
replaced vagrant with unity in examples referencing the pkg
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
Merge pull request #6141 from rolandwalker/doc_pkgutil_uninstall

doc: highlight `:pkgutil`
docs, error msgs, tests for depends_on :formula

replacing depends_on_formula in DSL
Update Alfred Cask to use https

Props @fly
update thunderbird to 31.1.1
Merge pull request #6153 from eugenesan/thunderbird

Update Thunderbird to 31.1.1
Merge pull request #6149 from vitorgalvao/rename-unity

Renamed unity3d to unity
Merge pull request #6138 from rolandwalker/doc_dsl_depends_on

docs, error msgs, tests for depends_on :formula