Add batch_size param to insert_batch(), update_batch()

This should resolve #42
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index 1a06bd5..7e72c23 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -7,6 +7,11 @@
 
 Release Date: Not Released
 
+-  :doc:`Query Builder <database/query_builder>`
+
+   -  Added a ``$batch_size`` parameter to the ``insert_batch()`` method (defaults to 100).
+   -  Added a ``$batch_size`` parameter to the ``update_batch()`` method (defaults to 100).
+
 Bug fixes for 3.0.5
 -------------------