Changed to regex when parsing scf filename

This is just a small change I had to make to be able to run this util. It would fail whenusing assembled fasta files with too many dots, eg. `A.Test_14_01.scf.fasta`
Is this going to treat the dot as a wildcard? Do you need to escape it with a backslash?
```python
match_expr = re.compile("(\S+)\.(scf|ctg)\.(fasta|fa)$", re.IGNORECASE)
```
I also added a `$` there, to tether to the end of the string though this is probably overkill.