fakeAsync tick does not mock the Date object

**Steps to reproduce and a minimal demo of the problem**
- Use fakeAsync in a test
- Create a variable with the current Date
- tick(2000) or any other number
- Create another variable with the current Date

**Current behavior**
The 2nd date is not the one you think it is

**Expected/desired behavior**
The 2nd date will be 2000ms later than the first one
