Unexpected parsing behaviour for List of strings containing a string with a numeric initial

This is just a report. I hope it will be useful for development. I'm using fire v0.4.0.

```python
# tmp.py
import fire
def main(keyword_list):
print([(keyword,type(keyword)) for keyword in keyword_list])
fire.Fire(main)
```
Will give you:
```
> python tmp.py --keyword_list=tmp,0
[('tmp', ), (0, )]

> python tmp.py --keyword_list=tmp,01
[('t', ), ('m', ), ('p', ), (',', ), ('0', ), ('1', )]

> python tmp.py --keyword_list=tmp,0tmp
[('t', ), ('m', ), ('p', ), (',', ), ('0', ), ('t', ), ('m', ), ('p', )]
```