feat(ngAnimate): provide support for staggering animations with CSS
fix($animate): ensure enable/disable animations work when the document node is used

Closes #4669
docs($provide): fix link to factory section
docs(guide): add link to book
docs(guide): improve links to books

Nested bullet points don't appear very nicely so resorted to nested
heading for the Learning Resources and in particular Books sections.

Closes #4677
Merge branch 'master' of https://github.com/angular/angular.js
componentizd!