Give script/proof the ability to be force-run. [ci skip]
Allow use of script/cibuild outside Travis. [ci skip]
Add push, pop, shift, and unshift Liquid filters.

Fixes #2892.
Release Jekyll :gem: v2.4.0
Merge pull request #2895 from jekyll/array-filters
Update history to reflect merge of #2895 [ci skip]
Merge pull request #2896 from jekyll/release-2-4

Release Jekyll :gem: v2.4.0
Add #2895 to release post.

#2896.
Release :gem: 2.3.0
Release :gem: 2.4.0
Update site history.
Point Liquid links to Liquid’s Github wiki
Provide a more helpful resource for questions like #2883