Feedback on Streams concept, similar to Ranges

[Andrew]

So I've been working on a small side project for the last few 
days, and I think that it's gotten to the point where I think 
that it's ready to be reviewed/critiqued.

The project is available on GitHub here: 
https://github.com/andrewlalis/streams

It introduces the concept of **Streams**, which is anything with 
either of the following function signatures:
- `int read(T[] buffer)` - this is an **input stream**.
- `int write(T[] buffer)` - this is an **output stream**.

The README.md on the project's homepage describes the motivation 
in more detail, but in short, I'm not 100% satisfied with Phobos' 
ranges, and I think that streams could be introduced as a 
lower-level primitive that's also more familiar to programmers 
coming from a variety of other languages, while still trying to 
be as idiomatically D as possible.

Just for the sake of demonstration, here's an example of using 
streams to transfer the contents of a file to some arbitrary 
output stream. Of course pretty much anything done with streams 
can also be done with ranges, but I think that the simpler 
interface will make some things more ergonomic.

```d
import streams;

void readFileTo(S)(string filename, S stream) if 
(isOutputStream!(S, ubyte)) {
   import std.stdio;
   auto fIn = FileInputStream(filename);
   transferTo(fIn, stream);
}
```

So, I'd appreciate if anyone could take a look at my project, 
tell me if you think this is a good idea or not, if I should 
introduce a DIP for this change if added to Phobos (I know the 
DIP process is closed at the moment), or if you have any other 
feedback for this.