Add calling vacuum to shrink_to and shrink_to_fit

HashMap::shrink_to_fit states "Shrinks the capacity of the map as much
as possible.".  Often, this is called to free up unused memory
allocations.  By calling vacuum here, this aligns with the intent

This also adds shrink_to and shrink_to_fit to ExpiringSet

src/lib.rs

@@ -225,16 +225,18 @@ impl<K: PartialEq + Eq + Hash, V> ExpiringMap<K, V> {
         self.inner.reserve(addtional);
     }
 
-    /// Shrink the internal map to the minimum allowable size
-    /// in accordance with the resize policy
+    /// Remove all of the expired entries and shrink the map to the minimum
+    /// allowable size in accordance with the resize policy
     pub fn shrink_to_fit(&mut self) {
+        self.vacuum();
         self.inner.shrink_to_fit();
     }
 
-    /// Shrink the internal map to the minimum of the
-    /// minimum allowable size and the `min_capacity`
-    /// in accordance with the resize policy
+    /// Remove all of the expired entries and shrink the map to the minimum of
+    /// the minimum allowable size and the `min_capacity` in accordance with the
+    /// resize policy
     pub fn shrink_to(&mut self, min_capacity: usize) {
+        self.vacuum();
         self.inner.shrink_to(min_capacity);
     }
 }
@@ -278,6 +280,18 @@ impl<K: PartialEq + Eq + Hash> ExpiringSet<K> {
             .filter(|(_, v)| v.not_expired())
             .map(|v| v.0)
     }
+
+    /// Shrink the set to the minimum allowable size in accordance with the
+    /// resize policy
+    pub fn shrink_to_fit(&mut self) {
+        self.0.shrink_to_fit();
+    }
+
+    /// Shrink the set to the minimum of the minimum allowable size and the
+    /// `min_capacity` in accordance with the resize policy
+    pub fn shrink_to(&mut self, min_capacity: usize) {
+        self.0.shrink_to(min_capacity);
+    }
 }
 
 impl<K: PartialEq + Eq + Hash, V> Default for ExpiringMap<K, V> {