chore(release): create script to undo a release for given number
feat(ngRoute): allow cancelling $route updates via $routeChangeEvent

Previously, one could perform this feat by listening to both
$locationChangeStart as well as $routeChangeStart, and being careful to update
the route correctly. Now, it's possible to simply preventDefault() on the
$beforeRouteChange event in order to prevent location and route from being
updated.

While this does not cancel $routeChangeStart, it does ensure that the correct
location is restored, and provides the same information as $routeChangeStart.

Closes #5855
Closes #5714
Closes #5581
test(ngRoute): fix wrong assertion in ngRoute suite

Previously, this was asserting that $beforeRouteChange was never called.
Prior to the preceeding commit, $beforeRouteChange didn't exist ---
however it is called during $locationChangeStart.

It looks like this test should be asserting that $routeChangeStart is
never fired.