Issue 32

- Refactored and extracted Snack and SnackContainer from SnackBar. 
- Users can new call new SnackBar().show() many times in an activity without problems. [#32](https://github.com/MrEngineer13/SnackBar/issues/32)

I think that new Snack(randomView); should work right but I'm not totally sure what the use case is.
> That said, are we sure we don't want 0 -> 1 -> 2 -> 3?
Yes, we can switch to a LinkedList instead of a Stack. I was worried that high priority snacks would not be shown first but there is already the capacity to show a snack immediately.