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.
There is also a problem with restoring in the right order. That will be fixed.