~/.bin/up.rs: fix compilation with new rust.

ugh, that was quite a thing. i guess that borrowing thing is still
confusing. why can't i get a read-only non-& value out of a vector?
and why does .as_slice() work?

.bin/up.rs

use std::os;
fn main() {
	let path = copy os::args()[1];
	let mut cwd = Path("");
	while cwd != Path("/") {
	let path = Path::new(os::args().get(1).as_slice());
	let mut cwd = Path::new("");
	while cwd != Path::new("/") {
		cwd = os::getcwd();
		if Path(path).exists() {
			io::println(cwd.to_str());
		if path.exists() {
			println!("{}", cwd.display());
			return;
		} else {
			os::change_dir(&Path(".."));
			os::change_dir(&Path::new(".."));
		}
	}