IE9+ Compatibility for `Date.now()`

It would probably be a good idea to cache the previous value and then return it afterwards. Or alternatively use a spy. The reason being you might rely on the value of Date.now() in a future tests, or randomly ordered tests, and this could cause you hidden problems.

You can spy like:

```
beforeEach ->
    spyOn(window.Date, "now").andReturn(undefined)
```

It will then only augment it for that one test