Fix `brew cask audit` not working without argument.

xcode: 8.3.1 is latest version.

missing_formula: fix undefined method `path` for nil:NilClass

formulary: Workaround for method missing for downcase on Pathname object

This check for a nil `tap` is necessary because Tap.from_path(path)
will simply return a nil value in the event the tap path is invalid

Our CI images are already updated with it.

gpg_spec test add 2.1.x compatibility

Virtualenv relocation fixes

Add probot-stale configuration.

Port audit_desc audit rules to a cop

audit: fix core formula alias check.

update-report: don't show new, installed formulae.

Was missing a formula object being passed.

These were those migrated from other taps but if they are installed
already: they aren't new to that user.

Revert "keg_relocate: Don't relocate dylib IDs containing metavariables."

Add Skylake to the Linux hardware list

java_requirement: Add newline to failure message

Signed-off-by: Bob W. Hogg <rwhogg@linux.com>

Xcode: update supported versions & download URLs for 8.3

Handle missing receipt on `brew install`.

For example if this is for a really old keg, keg where a user has
manually removed stuff or used `brew diy`.

ISSUE_TEMPLATE: tweak instructions.

Use `sudo` if parent path of `target` is not writable.

Be clearer about what's expected and where to file things.

ln_sf does the right thing when `dest` is a symlink pointing to a file:
the symlink gets overwritten with a link pointing to the new src. But
when dest points to a directory, we create a new symlink inside the
folder dest points to, which doesn't help us at all.

When we're assessing whether a bottle is relocatable, we shouldn't have
to descend into symlink paths we encounter. This is supposed to be the
default behavior but it doesn't appear to be (perhaps because we pass a
symlink to the keg on the command line?).

All of the switches that control this behavior differ between BSD and
GNU grep, so sniff the grep flavor first.