fix(ngAnimate): use a fallback CSS property that doesn't break existing styles

The clip property seems to remove the box-shadow property when an absolute
positioned animation is ongoing. This fix changes the property to be border-spacing
which is also very underused. The border-spacing CSS property is only visible
when border-collapse is set to separate.

Closes #4902
Closes #5030
Merge branch 'master' of https://github.com/angular/angular.js
componentizd!