A couple of minor improvements to connector-files

* read from FTP in binary mode for hash correctness
* tweak call to write to make it 8.0 compatible
32 is the md5sum hash length

When you run `md5sum file.csv` you get something like `5f7e1f1ff6096980d1be26ada2cd6b41  file.csv` which is what I used to create the md5 file and it took me some time to realize connector_file did expect the hash only.

That's why I suggest taking the first 32 chars as the hash.