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
Can you add the keyword "class"? It makes it more clear in the code that it is enum class and not c-type enum. 
I know you can write it like this but with the class keyword it is more evident
```enum class Socket ...```
```enum class Stream ...```
http://en.cppreference.com/w/cpp/language/enum