add missing include (#229)

cli.h

diff --git a/cli.h b/cli.h
index 08a59a6..af30061 100644
--- a/cli.h
+++ b/cli.h
@@ -19,6 +19,7 @@
 #include <numeric>
 #include <sstream>
 #include <limits>
+#include <cstdint>
 
 /**
  * Note this is a hastily hacked together command line parser.