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
Tests that should be added
1)   FileRecv::Stream::INTERRUPT
2)  FileRecv::Socket::INVALID
3) multithreaded receive from one sender. If you don't want to add a test for this please explain how it should be handled. 
4) process-to-process client-server test. I suggest you create an "example" directory where the binaries are. And maybe a simple bash script to run the example?. It is strictly not speaking a unit test but I don't see how you can unit test this.