Remove couchdb2file script

My thinking here is that the fact of writing to the local filesystem at all in this script is totally incidental. With any luck we'll be about to support filesystem-less streaming when we upgrade form node 0.8 to node 0.10. In the meantime it doesn't make much sense to try and abstract things to keep something possible that I don't intend on supporting much longer anyhow.

Similar, if not exactly the same, functionality that couchdb2file offered can be reproduced using curl and jq, like; `curl 'localhost:5984/mydb/_all_docs?include_docs=true' | jq -c '.rows | .[] | .doc'`