This allows custom rules to define an `excluded_match_kinds` array instead of listing out all but one or a few of the `SyntaxKind`s in `match_kinds`. Rules that include both `match_kinds` and `excluded_match_kinds` will be invalid, since there's not an obvious way to resolve the two without an arbitrary priority between them.
The MIT license doesn't require that all files be prepended with this
licensing or copyright information. Realm confirmed that they're ok with this
change. This will enable some companies to contribute to SwiftLint and the
date & authorship information will remain accessible via git source control.
JP Simard