Fix build errors on nightly (alloc crate changes)

Author: dhardy

src/distributions/other.rs

@@ -180,7 +180,7 @@ impl<T> Distribution<Wrapping<T>> for Standard where Standard: Distribution<T> {
 mod tests {
     use {Rng, RngCore, Standard};
     use distributions::Alphanumeric;
-    #[cfg(all(not(feature="std"), feature="alloc"))] use alloc::String;
+    #[cfg(all(not(feature="std"), feature="alloc"))] use alloc::string::String;
 
     #[test]
     fn test_misc() {

src/distributions/weighted.rs

@@ -15,7 +15,7 @@ use ::core::cmp::PartialOrd;
 use ::{Error, ErrorKind};
 
 // Note that this whole module is only imported if feature="alloc" is enabled.
-#[cfg(not(feature="std"))] use alloc::Vec;
+#[cfg(not(feature="std"))] use alloc::vec::Vec;
 
 /// A distribution using weighted sampling to pick a discretely selected item.
 ///

src/seq.rs

@@ -15,10 +15,11 @@
 #[cfg(feature="alloc")] use core::ops::Index;
 
 #[cfg(feature="std")] use std::vec;
-#[cfg(all(feature="alloc", not(feature="std")))] use alloc::{vec, Vec};
+#[cfg(all(feature="alloc", not(feature="std")))] use alloc::vec;
+#[cfg(all(feature="alloc", not(feature="std")))] use alloc::vec::Vec;
 // BTreeMap is not as fast in tests, but better than nothing.
 #[cfg(feature="std")] use std::collections::HashMap;
-#[cfg(all(feature="alloc", not(feature="std")))] use alloc::btree_map::BTreeMap;
+#[cfg(all(feature="alloc", not(feature="std")))] use alloc::collections::BTreeMap;
 
 
 use super::Rng;
@@ -599,7 +600,7 @@ mod test {
     #[cfg(feature = "alloc")] use {Rng, SeedableRng};
     #[cfg(feature = "alloc")] use prng::XorShiftRng;
     #[cfg(all(feature="alloc", not(feature="std")))]
-    use alloc::Vec;
+    use alloc::vec::Vec;
 
     #[test]
     fn test_slice_choose() {