add subsection slides

header.tex

@@ -79,3 +79,11 @@
     \tableofcontents[currentsection]
   \end{frame}
 }
+
+\AtBeginSubsection[]
+{
+  \begin{frame}
+    \frametitle{Table of Contents}
+    \tableofcontents[currentsection, currentsubsection]
+  \end{frame}
+}