file io

- We still need to come up with a naming metaphor for this!
- it is a pipeline communication to stream a file from a server to a client.
- It follows a model similar to: http://zguide.zeromq.org/c:fileio3
It is very much c-style passing of return values.  The problem is to understand what the return values stand for. 
I think a clearer way is to return type safe ```class enums```.