Add new page
A little more work.
updates to CI page. [ci skip]
Finish CI guide.
Fixes, fixes.
html-proof ~> htmlproof
Speak English good. h/t @gjtorikian
Merge pull request #2432 from jekyll/docs-4-ci
Update history to reflect merge of #2432 [ci skip]
Spike out jekyll <cmd> --watch into a separate gem.
Use bundle exec in CI guide. [ci skip]

h/t @ndarville
Ref: #2432
Merge pull request #2550 from jekyll/extract-watch
Update history to reflect merge of #2550 [ci skip]