fix($http): update httpBackend to use ActiveXObject on IE8 if necessary

window.XMLHttpRequest is not always available in IE8 despite it not running in quirks mode,
in which case Angular should be using the ActiveXObject instead. Just checking the browser
version is taking too many shortcuts.

Closes #5677
Closes #5679
fix(http): make jshint happy
docs(animations): ngClass usage should link to ngClass documentation

Fixing reference to ngClass documentation

Closes #6089
fix(ngResource): don't append number to '$' in url param value when encoding URI

Previously, if a URL parameter value included a $, it would replace the dollar sign with a literal
'$1' for mysterious reasons. Using a function rather than a replacement string circumvents this
behaviour and produces a more expected result.

Closes #6003
Closes #6004
docs(changelog): release notes for 1.2.11
chore(release): cut v1.2.11 release
chore(release): start v1.2.12 (1.2.12)
chore(release): update cdn version
chore(ngClass): remove debugger statement from an e2e test
fix(mocks): always call functions injected with `inject` with `this` set to the current spec

Currently when a function is injected inside of a test we set the context to undefined which
is a bug.

Closes #6102