Fix typo causing scss error.
Merge pull request #677 from jcushman/scss-fix

Fix typo causing scss error.
SCSS fix and cleanup.

- Fix typo causing sass compile error.
- Move duplicated CSS in style-responsive.scss and
style-responsive-archive.scss into global.scss.
- Move 3rd-party files into css/lib.
- Remove duplicative css includes in templates.
Merge branch 'css-cleanup2' of https://github.com/jcushman/perma into css-cleanup2