CSS licensing

Some of the css files in the templates seem to be licensed under Apache 2 while others seem to be bound by CC SA 4 as specified in the main license file being that there are no headers in the files.

The ones which have Apache headers are:
https://github.com/google/material-design-lite/blob/mdl-1.x/templates/android-dot-com/styles.css
https://github.com/google/material-design-lite/blob/mdl-1.x/templates/article/styles.css
https://github.com/google/material-design-lite/blob/mdl-1.x/templates/dashboard/styles.css
https://github.com/google/material-design-lite/blob/mdl-1.x/templates/text-only/styles.css

The ones without headers are:
https://github.com/google/material-design-lite/blob/mdl-1.x/templates/blog/styles.css
https://github.com/google/material-design-lite/blob/mdl-1.x/templates/portfolio/styles.css

If they were all licensed under Apache 2, that would make it much easier to use the CSS in Apache projects. Were the two files without Apache headers an oversight, or was that a conscious decision?

If it was an oversight, I'd be happy to create a pull request.