Pin npm-shrinkwrap to v5.0.0 so that it works with npm 2.x.

Fixes #15105.
give all docs callouts IDs

[skip sauce]
Fix a small grammar mistake.

[ci skip]
Merge pull request #15121 from twbs/npm-shrinkwrap@5.0.0

Pin npm-shrinkwrap to v5.0.0 so that it works with npm 2.x.
Merge pull request #15093 from twbs/id-callouts

Give all docs callouts IDs
[skip sauce]
bump remarkable devDependency to ~1.4.1

[skip sauce]
Merge pull request #15122 from twbs/bump-remarkable

bump remarkable devDependency to ~1.4.1
clarify that Bower is one among several installation methods
Fix link
Merge pull request #15126 from Quy/master

Fix link
Specify `img` dimensions in the HTML.
Tweak colors to improve accessibility.
Accessibility improvements.