Integrate phpcs-patch into Travis and pre-commit hook

[westonruter]

We need to facilitate only reporting PHP_CodeSniffer issues for lines that are part of changes in the pull request (on Travis) or as part of the current commit (Travis or pre-commit hook).

This depends on xwp/PHP_CodeSniffer#5

When running on Travis, we need to look at the TRAVIS_COMMIT_RANGE environment variable. For pre-commit, we obviously just look at the stage.

The work here is needed for integrating PHP_CodeSniffer into the WordPress Core build tools (#30153).

[westonruter]

I've worked out a way for Travis to filter PHP_CodeSniffer and JSHint issues just to issues reported on the changes within a PR: #95.