csv -H on output should remove the header row.

For instance, if there’s a header row in the input csv, but I don’t want to output it:

```
/csv/head/csv -H/?url…
```

This is of course equivalent to:

```
/csv -H/delete 0/head/csv/?url…
```

This is really just for consistency of `csv` options on input and output.

Refs #12 and #35.