Ability use args, kwargs with delimiter

Fire now try to parse flat args and kwargs, but often this not convenient
Example:

```
import fire

def test(*args, **kwargs):
print(kwargs)
print(args)

fire.Fire(test)

```

`python main.py arg1 arg2 --kwarg1 1 --kwarg2 2`

`
{'kwarg1': 1, 'kwarg2': 2}
('arg1', 'arg2')
`

In some cases will be much more simple have opportunity to set *args **kwargs like this :
`
python main.py --args arg1 --args arg2 --kwargs kwarg1=1 --kwargs kwarg2=2
`