Update to reveal.js 4.1.2 (#136)

- New tools/ script to manually keep step for updates
- Plugins are all updated
- Template update following latest Pandoc version
- updated README for documentation
- Help page updated 
- See other change in NEWS file
diff --git a/inst/reveal.js-4.1.2/test/assets/external-script-d.js b/inst/reveal.js-4.1.2/test/assets/external-script-d.js
new file mode 100644
index 0000000..1c5925b
--- /dev/null
+++ b/inst/reveal.js-4.1.2/test/assets/external-script-d.js
@@ -0,0 +1 @@
+window.externalScriptSequence += 'D';
\ No newline at end of file