Clarifies use of g++, closes #2014

Author: JJ

README.md

@@ -71,7 +71,13 @@ To build the documentation web pages, simply run:
 
 Please note that you will need to have [nodejs](https://nodejs.org)
 installed to produce HTML content with the above command, in particular
-a `node` executable should be in your `PATH`.
+a `node` executable should be in your `PATH`. Besides, you will need
+to have `g++` installed in order to build some of the dependencies
+that are installed with nodejs. nodejs is needed only to apply
+highlighting to the included code; if you do not want that, simply
+write 
+
+    $ make html-nohighlight
 
 After the pages have been generated, you can view them on your local
 computer by starting the included `app.pl` program: