Fix alloc feature

Author: dhardy

src/iter.rs

@@ -195,7 +195,7 @@ impl<'a, R:?Sized+'a, U, F> Iterator for FlatMap<'a, R, U, F>
 mod tests {
     use {Rng, RngCore};
     use distributions::{Uniform};
-    #[cfg(features="alloc")] use alloc::{Vec, String};
+    #[cfg(all(not(feature="std"), feature="alloc"))] use alloc::{Vec, String};
 
     #[test]
     #[cfg(any(feature="std", feature="alloc"))]

src/lib.rs

@@ -252,7 +252,7 @@
 #![cfg_attr(all(target_arch = "wasm32", not(target_os = "emscripten")), recursion_limit="128")]
 
 #[cfg(feature="std")] extern crate std as core;
-#[cfg(all(feature = "alloc", not(feature="std")))] extern crate alloc;
+#[cfg(all(feature = "alloc", not(feature="std")))] #[macro_use] extern crate alloc;
 
 #[cfg(test)] #[cfg(feature="serde-1")] extern crate bincode;
 #[cfg(feature="serde-1")] extern crate serde;
@@ -1128,8 +1128,7 @@ pub fn sample<T, I, R>(rng: &mut R, iterable: I, amount: usize) -> Vec<T>
 mod test {
     use mock::StepRng;
     use super::*;
-    #[cfg(feature="alloc")]
-    use alloc::boxed::Box;
+    #[cfg(all(not(feature="std"), feature="alloc"))] use alloc::boxed::Box;
 
     pub struct TestRng<R> { inner: R }