Why no io.Reader and io.Writer interface for snappy?

```
Interested to find out why there's no streaming interface for snappy?  Wouldn't 
the protocol support it?  Would be nice to know that data streams could use 
snappy too like the json stuff: `json.NewEncoder(w).Encode(obj)` 
```

Original issue reported on code.google.com by `m...@stretchr.com` on 25 Jul 2014 at 5:20
