refactor(collapse): use ngAnimate

- Animations are now opt-in, include ngAnimate to see collapse animations, otherwise, leave them out and collapse works fine without animation

- ngAnimate handles initial state and doesn't animate if first reflow hasn't occurred.
  https://github.com/angular/angular.js/commit/cc5846073e57ef190182026d7e5a8e2770d9b770

- Tests may need more work. Right now they test for 'in' class.

This is my attempt at #1274 .