docs(CHANGELOG): add v1.2.3 changes
chore(release): cut 1.2.3 unicorn-zapper release
chore(release): start 1.2.4 wormhole-baster iteration
docs(migration): add a note about "private" properties being reverted

Closes #5086
docs(guide/compiler): add fourth step on appending the compiled template to the DOM

Closes #5087
docs(guide/providers): fix typo

Closes #5102
docs(guide/di): use square bracket notation for $inject annotation

Closes #5104
docs($injector): use square bracket notation for $inject annotation

Closes #5104
docs($window): move use of $window to controller

Move use of `$window` from template to controller, because accessing `$window`
in expressions is now disallowed and doesn't work.

Closes #5110
docs(guide/concepts): fix incorrect module name in example

Closes #5116
docs(form): provide a list of Angular's built-in validation tokens

As requested by a top-rated Disqus comment: http://docs.angularjs.org/api/ng.directive:form.FormController#comment-655325797

Closes #5121
docs(tutorial/step-0): add target="_blank" to open app in new page

Closes #5145
docs(tutorial/step-12): fix typo

Closes #5148
docs($compile): fix missing space
docs(tutorial/step-10): fix typo

Closes #5171
chore(docs): fix back-to-top anchor in angularjs.org doc pages

Closes https://github.com/angular/angularjs.org/issues/45
docs($animate): require ngAnimate in example, syntax fixes

The example in the section "JavaScript-defined Animations" would not run without the ngAnimate dependency. Also added a missing comma and semicolons.
chore(grunt): update to latest jshint task

Upgrade JSHint task from ~0.6.4 to ~0.7.2. Two useful changes: ability
to set jshintrc option to use jshint's native ability for finding .jshintrc
files relative to the linted files and update jshint to 2.3.0.

Closes #5143
chore(travis): use only websockets and xhr-polling

I wanna see more info about BrowserStack...
chore(travis): tolerate 2 disconnects to make the build more stable