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.
I want to double check the expected behavior.

I call show 0 and while that is showing show in this order 1, 2, 3. Currently in the play store app you will see 0 -> 3 -> 2-> 1. 

This one has a bug and does 0 -> 2 -> 1 -> 0 which I will fix. That said, are we sure we don't want 0 -> 1 -> 2 -> 3?