Given two things, one of which implements std::io::Read and other implements std::io::Write, make a single socket-like object which implmenets Read + Write. Note that you can't write to it while waiting for data to come from read part.
Example: generate a virtual socketpair.
```rust fn main() { extern crate pipe; extern crate readwrite;
let (r1,w1) = pipe::pipe();
let (r2,w2) = pipe::pipe();
let (s1,s2) = (ReadWrite::new(r1,w2), ReadWrite::new(r2,w1));
} ```