chore(release): start 1.2.3 unicorn-zapper iteration
chore: update copyright year in file headers
chore(docs): remove Disqus comments

We don't actively moderate these comments, and they range from
out of date, to inflammatory, to spam. Going forward, improvements
to the docs should be done via a PR, and questions should go on
StackOverflow where they can be curated and kept up to date by
AngularJS developers who help out there.
fix(input): Support form auto complete on modern browser

Although modern browser support the "input" event, they still only fire
the "change" event when they auto complete form elements
other than the currently selected one.

Related to #1460
fix($animate): ensure blocked keyframe animations are unblocked before the DOM operation

Closes #5106