Use Float trait from num crate

Cargo.toml

@@ -22,6 +22,7 @@ arbitrary = ["quickcheck"]
 [dependencies]
 rustc-serialize = "*"
 rand = "*"
+num = "*"
 
 [dependencies.quickcheck]
 optional = true

src/lib.rs

@@ -87,6 +87,7 @@ Feel free to add your project to this list if you happen to use **nalgebra**!
 
 extern crate rustc_serialize;
 extern crate rand;
+extern crate num;
 
 #[cfg(feature="arbitrary")]
 extern crate quickcheck;

src/traits/structure.rs

@@ -1,9 +1,9 @@
 //! Traits giving structural informations on linear algebra objects or the space they live in.
 
 use std::{f32, f64, i8, i16, i32, i64, u8, u16, u32, u64, isize, usize};
-use std::num::Float;
 use std::slice::{Iter, IterMut};
 use std::ops::{Add, Sub, Mul, Div, Rem, Index, IndexMut};
+use num::Float;
 use traits::operations::{RMul, LMul, Axpy, Transpose, Inv, Absolute};
 use traits::geometry::{Dot, Norm, Orig};