Update to the last Rust.

Version of rustc: 0.10-pre (b0ce960 2014-02-17 22:16:51 -0800)
This replaces uses of the `Orderable` trait by a `PartialOrd` trait: the `min` and `max` methods
are replaced by `inf` and `sup` methods.
Vectors do not implement the `Ord` trait any more.

Fix #4