fix(angular.copy): Fix angular.copy not copying non-index properties of array

Old implementation didn't copy non-index properties correctly, causing
arrays to not be fully copied. This commit fixes that problem by
modifying angular.copy's code to handle arrays by using a 'for in' loop
rather than a regular for loop.

Closes #5238
Merge branch 'fix-angular.copy' of http://github.com/shanepelletier/angular.js into fix-angular.copy