Update README

Author: baopham

README.md

@@ -20,10 +20,10 @@ Supports all key types - primary hash key and composite keys.
   * [Conditions](#conditions)
   * [all() and first()](#all-and-first)
   * [Pagination](#pagination)
-  * [Update](#update) / [updateAsync()](#updateasync)
-  * [Save](#save) / [saveAsync()](#saveasync)
-  * [Delete](#delete) / [deleteAsync()](#deleteasync)
-  * [Chunk](#chunk)
+  * [update](#update) / [updateAsync()](#updateasync)
+  * [save](#save) / [saveAsync()](#saveasync)
+  * [delete](#delete) / [deleteAsync()](#deleteasync)
+  * [chunk](#chunk)
   * [limit() and take()](#limit-and-take)
   * [firstOrFail()](#firstorfail)
   * [findOrFail()](#findorfail)