Allow unstable items.

Some of them don't have any stable equivalent yet.

src/lib.rs

@@ -81,7 +81,7 @@ Feel free to add your project to this list if you happen to use **nalgebra**!
 #![deny(non_upper_case_globals)]
 #![deny(unused_qualifications)]
 #![deny(unused_results)]
-// #![allow(unstable)]
+ #![allow(unstable)]
 #![warn(missing_docs)]
 #![feature(old_orphan_check)]
 #![feature(unboxed_closures)]

tests/assert.rs

@@ -1,6 +1,7 @@
 //! Assertion macro tests
 
 #![feature(plugin)]
+#![allow(unstable)]
 
 #[plugin]
 #[macro_use]