[WIP] Add StreamResponse

I add all things needed for StreamResponse, it remains the following things to do : 

- Test
- Set the correct protocol version where it's needed 

The implementation work like this  : 

Response has a new method : read which accept a callback with one parameter, this function is call each time new content arrive, and new content is the first parameter of this callback.

By default Response call only once this callback with all content, when a response is chunked, it's create a StreamResponse object instead of Response and when using read function the callback is call each time a new chunked is received.