include a copy of the CC-BY 3.0 License that the docs are under

downloaded from http://creativecommons.org/licenses/by/3.0/legalcode.txt
Fix a silly typo
Merge pull request #10743 from hnrch02/patch-1

Fix a silly typo
fix #10737
Merge pull request #10693 from twbs/include-docs-license

include a copy of the CC-BY 3.0 License that the docs are under
Remove unused variables.
Lint assets/js/application.js and assets/js/customizer.js.
Update holder.js to v2.1.0.