Bump to v4.0.0.

internal/stackGet.js

@@ -0,0 +1,19 @@
+import assocGet from './assocGet';
+
+/**
+ * Gets the stack value for `key`.
+ *
+ * @private
+ * @name get
+ * @memberOf Stack
+ * @param {string} key The key of the value to get.
+ * @returns {*} Returns the entry value.
+ */
+function stackGet(key) {
+  var data = this.__data__,
+      array = data.array;
+
+  return array ? assocGet(array, key) : data.map.get(key);
+}
+
+export default stackGet;