Ideally, SwiftLintCore would some day only contain components
that are needed to define rules. Consequently, it would be the
only bundle required to import for (external) rule development.
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.