New Release: 2.9.1

Following the revocation of version 2.9.0, we observed an extended "release candidate" phase where we encouraged users to vet JSHint for undesirable changes in behavior. During that time, we identified and resolved a number of such regressions. This release comprises all changes from the release candidate phase along with the improvements initially released as version 2.9.0. This release does not itself contain any changes to the codebase. If you are upgrading from version 2.8.0 or earlier, please refer to the previously-published release notes for details on bug fixes and features--these can be found in the project's file and on the project's website.