Feature/fix bug in save id table tsv

With a bug, an output of ".maf_id_table.tsv" looked like:

```
<built-in function id>  {'C': 0.001, 'B': -1, 's': 0}
<built-in function id>  {'C': 0.001, 'B': -1, 's': 1}
<built-in function id>  {'C': 0.01, 'B': -1, 's': 0}
<built-in function id>  {'C': 0.01, 'B': -1, 's': 1}
```

I fixed it to output id numbers.