Import std::num::Float explicitly.

It was removed from the prelude as part of <rust-lang/rust#18827>.

Author: Ms2ger

src/approxeq.rs

@@ -7,6 +7,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use std::num::Float;
 
 /// Trait for testing approximate equality
 pub trait ApproxEq<Eps> {
@@ -44,4 +45,4 @@ impl ApproxEq<f64> for f64 {
     fn approx_eq_eps(&self, other: &f64, approx_epsilon: &f64) -> bool {
         (*self - *other).abs() < *approx_epsilon
     }
-}
+}