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out of date, to inflammatory, to spam.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
docs(CONTRIBUTING): consolidated submitting PRs sections
docs(CONTRIBUTING): highlight what makes a good issue submission
docs(CONTRIBUTING): fix typo
fix(ngAnimate): ensure animations are disabled upon bootstrap for structrual animations

Closes #5130
docs(CONTRIBUTING): add link to github-pr-helper
chore: add script for updating bower repos
chore(travis): let's give BrowserStack a try

Switch the build to use BrowserStack instead of SauceLabs.

This also adds IE11 to our build.
chore(travis): add some more info for BrowserStack sessions
refactor(angular.js): improve trim performance

According to Flagrant Badassery's blog
http://blog.stevenlevithan.com/archives/faster-trim-javascript
and this comparison http://jsperf.com/trim-function, this trim method is faster.

Closes #4406
docs(guide/scope): access the current element's scope in the console.

Closes #4884
docs(CONTRIBUTING): fix broken link to GitHub PR Helper

Closes #5134
docs(compile): fix typo

Closes #5133
chore(changelog): remove tmp file
chore(mocks): wrap angular-mocks.js in closure

Closes #5080
chore($httpBackend): preserve original non-zero http status code for file:// apps

Previously if an app was running from file:// origin we would always return either
http 200 or 404 depending on whether the response was present.

This changes the behavior so that we do this only if the protocol of the request
(not the origin) is file:// and only if the status code is 0.

Closes #4436
Closes #4587
Closes #4514