fix($interval): when canceling, use clearInterval from $window instead of global scope.

In $interval.cancel, use clearInterval from the $window service instead of from global scope.
The variable clearInterval declared above isn't visible here.
test($interval): add tests making sure $interval uses the methods from $window
docs(Getting Started): fix typo

Closes #8015
docs(guide/$location): fix a typo

Change "window.location.path" to "window.location.pathname".

Closes #8012
docs($rootScope): fix incorrect param name in $watchGroup description

Closes #7834
style(Angular.js): remove extra whitespace