Merge pull request #299 from cuviper/refactor-entry

Refactor and shrink `Entry`

Author: cuviper

src/map.rs

@@ -462,7 +462,7 @@ impl<K, V, S> IndexMap<K, V, S>
 where
     S: BuildHasher,
 {
-    fn hash<Q: ?Sized + Hash>(&self, key: &Q) -> HashValue {
+    pub(crate) fn hash<Q: ?Sized + Hash>(&self, key: &Q) -> HashValue {
         let mut h = self.hash_builder.build_hasher();
         key.hash(&mut h);
         HashValue(h.finish() as usize)