Close #13 save bad rows to a file

[dimus]

This PR is about #13 feature request.
It is my first Rust exercise, would be great to learn how does it go.

[emk]

Thank you for a great patch, and my apologies for a slow response! I'm going to revisit scrubcsv sometime in the next couple of weeks, and when I do, I'm going to tweak your patch slightly and include it.

Your Rust code looks great!

[ngirard]

This would be nice to have ;-)

[jtara1]

I'm getting an error when it attempts to write malformed rows to the file.

$ scrubcsv -d $'\t' --bad-rows-path temp.tsv input.tsv > /dev/null
ERROR: cannot write record
  caused by: CSV error: found record with 102 fields, but the previous record has 107 fields

Would it make more sense to append malformed rows to a file than to use a csv writer to append which validates it's csv?