Move Cask’s vendored `plist` to `Homebrew/vendor`.

Make -no_weak_imports opt-in.

Revert "diagnostic: ignore duplicated `brew-cask` commands"

The experiment to add `-no_weak_imports` unconditionally has been a bit
of a failure. It's broken more than it's fixed and I don't think we can
have this as a default for Xcode 8.

Add `ENV.no_weak_imports` to be used by formulae authors and make
`ENV.no_weak_imports a no-op (for now).

We may reconsider this behaviour in future.

Forgot renaming `cab-container`.

Cask Refactoring

Add atom language plugin to docs

Refactor `shutup`.

add .editorconfig

build: permit weak imports in Go reverse deps.

Make "brew man" also generate Cask's manpage.

Go makes extensive use of weak imports so we need to allow them when
building Go-using software.

Closes https://github.com/Homebrew/homebrew-core/issues/4047.

Also, check in this manpage, adjust the Rakefile and remove the old one.

Fixes #731.

bump-formula-pr: return to starting branch

bump-formula-pr now creates non-tracking branches

Remove LOAD_PATH warning from Hbc::CLI::Doctor.

Install Cask’s default tap if untapped.

Use dummy containers for cask tests.

Remove Cask developer scripts.

After branching, bumping, pushing, and pr-ing; return to whatever branch
was originally checked out.

In most cases, I'd imagine users to want to continue receiving tap
updates from master. However, after using bump-formula-pr, the tap in
which the formula was bumped is left on the working branch that was
doing the bumping and pull-request. After opening the PR, we should
return to whatever branch the user originally had checked out – most
likely master. (But git allows us to just say "previous branch" by using
`-`)