After Issue #985 was merged, bottles for Mavericks are no longer
being built, meaning installations are triggering builds.

Update the FAQ to show that builds will most likely now be
triggers on Mavericks since their bottles are not being generated.

Use `launchctl` to get running processes by bundle ID.

xcode: cleanup Xcode::Version usage.

Don't wrap `MacOS.version` which does comparisons properly already and
avoid stupidly long lines.

Refactor Cask installer.

Fail if cask source already exists.

travis: use Xcode 8.1 on Sierra.

added "CLT" abbreviation after "Command Line Tools" in Installation.md doc

For code coverage from `brew test-bot`.

added 'CLT' abbreviation after 'Command Line Tools' (so that if someone follows link to footnote#3, the meaning of 'CLT' in footnote is clear)

bash_test: handle race condition.

Other tests may delete Bash files (e.g. `shcmd.sh`) while tests are
ongoing so ensure this doesn't cause a test failure.

fs_leak_logger: use more permissive mkpath.

tap-new: use latest Travis CI recommended config.

travis.yml: enable macOS builds again.

This avoids a race condition occurring here.

Pretty sure no-one cares about this except me but this works
consistently across a variety of different taps and is faster than the
old version.

uninstall_test: require testing_env

update.sh: Use full path to pkill

Fixes #1600.

Fix macOS version comparison

docs/Checksum_Deprecation.md: Note that SHA-1 now blocks installation

dependency_collector: Make ant_dep and xz_dep public

They were already public on macOS, but they were made
private by mistake on all other platforms.
DependencyCollector.tar_needs_xz_dependency? depends
on xz_dep being public, so there's no turning back now :(

rubocop: exclude more files.