fix(ngView): accidentally compiling leaving content

closes: #2304
feat(injector): add has method for querying

Closes #2556
fix(ngAnamite): eval ng-animate expression on each animation
fix($location): prevent navigation if already on the URL
fix($location): compare against actual instead of current URL
feat(ngInclude): $includeContentRequested event

Adding a $includeContentRequested event in order to better keep track of
how many includes are sent and be able to compare it with how many have
finished.
docs(injector): add docs for $injector.has
fix($location): prevent navigation when event isDefaultPrevented
doc(input): fix small typo in code example