fix($animate): use a scheduled timeout in favor of a fallback property to close transitions

With ngAnimate, CSS transitions, that are not properlty triggered, are forceably closed off
by appling a fallback property. The fallback property approach works, however, its styling
itself may effect CSS inheritance or cause the element to render improperly. Therefore, its
best to stick to using a scheduled timeout to run sometime after the highest animation time
has passed.

Closes #5255
Closes #5241
Closes #5405
style(animateSpec): ensure spacing between specs and describes is consistent
feat(jqLite): provide support for element.one()
feat(ngAnimate): provide configuration support to match specific className values to trigger animations

Closes #5357
Closes #5283
docs(CHANGELOG): add v1.2.6 changes
chore(release): improve the release script
chore(release): cut v1.2.6 release
chore(release): start v1.2.7
chore(release): add codename for 1.2.7
docs(guide): fix typo

Closes #5481
chore(release): update cdn version
style($http): fix a semi-colon
feat(input): evaluate exprs for  ngTrueValue/ngFalseValue

If ngTrueValue / ngFalseValue are strings, they are evaluated as expressions.
If the resulting value is undefined, and not the "undefined" constant, then it is
treated as a string literal. Otherwise, the evaluated value is used.

If no string expression is provided, then the default value remains true or false.