docs(ngModelController): fix $asyncValidators example

Also fixes a typo (◜௰◝)

Closes #8906
chore(shrink-wrap): update shrinkwrap to latest benchpress
docs(CHANGELOG.md): add breaking change for a9fcb0d0 (v1.2.13)

Closes #8909
docs(ngSwitch): fix priority
docs(ngBlur): explain blur events
docs(interpolate): fix link text
docs(tutorial/step_05): improve formatting of code identifier

Closes #8557
docs(README): fix 'Contribution guidelines' link

The current link leads to a page 'Building and Testing AngularJS'.
This same link is also included in the 'Building AngularJS' section
of the README where it's more relevant.
docs($sce:unsafe): fix link to $sce docs

The second link to Strict Contextual Escaping (SCE) points to a 404.

Closes #8514
docs(docs.css): improve comma spacing in TOC on mobile
fix(numberFilter): format numbers that round to zero as nonnegative

Previously when a negative number was rounded to 0 by the number filter
it would be formated as a negative number.  This means something like
{{ -0.01 | number: 1 }} would output -0.0.  Now it will ouput 0.0
instead.

Closes #8489