[WIP] Running the test suite on more platforms

_Pease consider this PR as a work in progress_

We want to enable the testing on more browsers / platforms thanks to SauceLabs.

I would need some help to fix the tests for Safari (I don't have a Mac available). To start with, checking the issues with the animation would help (other issues might also be observe on IE and I'll try to fix them).

@codelogic @mhevery @jbdeboer could any of you look at the issues on Safari ?

Todos:
- [ ] Fix unit tests on IE,
- [ ] Fix unit tests on Safari,
- [ ] Check (and fix when needed) e2e test on IE & Safari
- [ ] Re-enable all platforms