Added has() method to auto.IInjectorService

Angular added the has() method to $injector in version 1.2 (see: https://github.com/angular/angular.js/blob/g3_v1_2/src/auto/injector.js)
angularjs revert marking arguments for link function as optional
Merge pull request #1650 from JohnKurlak/master

Added has() method to ng.auto.IInjectorService
Correct ICustomScope reference
Merge pull request #1655 from mjibson/patch-1

angularjs: docs: Correct ICustomScope reference