minor fix for https

diff --git a/trex_book-docinfo.html b/trex_book-docinfo.html
index a444f50..c050287 100755 (executable)
--- a/trex_book-docinfo.html
+++ b/trex_book-docinfo.html
@@ -1,5 +1,5 @@
 
-<script src="http://d3js.org/d3.v3.min.js" charset="utf-8"></script>
+<script src="https://d3js.org/d3.v3.min.js" charset="utf-8"></script>
 
 <script src="my_chart.js"></script>