Bump to v4.0.0.

internal/hashSet.js

@@ -0,0 +1,18 @@
+import nativeCreate from './nativeCreate';
+
+/** Used to stand-in for `undefined` hash values. */
+var HASH_UNDEFINED = '__lodash_hash_undefined__';
+
+/**
+ * Sets the hash `key` to `value`.
+ *
+ * @private
+ * @param {Object} hash The hash to modify.
+ * @param {string} key The key of the value to set.
+ * @param {*} value The value to set.
+ */
+function hashSet(hash, key, value) {
+  hash[key] = (nativeCreate && value === undefined) ? HASH_UNDEFINED : value;
+}
+
+export default hashSet;