fix(ngAnimate): defer DOM operations for changing classes to postDigest

When ngAnimate is used, it will defer changes to classes until postDigest.
Previously, AngularJS (when ngAnimate is not loaded) would always immediately
perform these DOM operations.

Now, even when the ngAnimate module is not used, if $rootScope is in the midst
of a digest, class manipulation is deferred. This helps reduce jank in
browsers such as IE11.

/CC @tbosch --- alternative/more general fix here

Closes #8234
Closes #9263
there is #8946 which changes the behavior in ngAnimate to exactly what @gkalpak proposed. @matsko is implementing it for rc5. so we should change this PR to do the same.