Allow placeholders in permalinks
Remove duplicate code
The jsonify filter should deep-convert to Liquid when given an Array.

Fixes https://github.com/github/choosealicense.com/issues/225
Merge pull request #3032 from jekyll/jsonify-deeply
Update history to reflect merge of #3032 [ci skip]
Implement @parkr's suggestions
Merge pull request #3031 from alfredxing/frontmatter-permalinks
Update history to reflect merge of #3031 [ci skip]
Update continuous-integration.md

Fix miswording
Merge pull request #3040 from mitaa/master
Update history to reflect merge of #3040 [ci skip]
Add Sass mixins and use them.

Reduces code duplication and makes things cleaner.
Move custom code from _font-awesome.scss to _style.scss.

Also change the order of includes so that _style.scss is last for precedence reasons.