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]
Docs: use font-awesome for permalink too.

Also remove the unused `permalink` class from the `a` tag.