fix(rustup): update io import, Writer::write

Make it build with the latest rust-nightly (2015-01-27)

Renamed io import to old_io.
Renamed Writer::write to Writer::write_all

examples/client.rs

@@ -2,8 +2,8 @@
 extern crate hyper;
 
 use std::os;
-use std::io::stdout;
-use std::io::util::copy;
+use std::old_io::stdout;
+use std::old_io::util::copy;
 
 use hyper::Client;