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/examples/backgrounds.html b/inst/reveal.js-4.1.2/examples/backgrounds.html
new file mode 100644
index 0000000..19d40c3
--- /dev/null
+++ b/inst/reveal.js-4.1.2/examples/backgrounds.html
@@ -0,0 +1,141 @@
+<!doctype html>
+<html lang="en">
+
+	<head>
+		<meta charset="utf-8">
+
+		<title>reveal.js - Slide Backgrounds</title>
+
+		<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no">
+
+		<link rel="stylesheet" href="../dist/reveal.css">
+		<link rel="stylesheet" href="../dist/theme/serif.css" id="theme">
+		<style type="text/css" media="screen">
+			.slides section.has-dark-background,
+			.slides section.has-dark-background h2 {
+				color: #fff;
+			}
+			.slides section.has-light-background,
+			.slides section.has-light-background h2 {
+				color: #222;
+			}
+		</style>
+	</head>
+
+	<body>
+
+		<div class="reveal">
+
+			<div class="slides">
+
+				<section data-background="#00ffff">
+					<h2>data-background: #00ffff</h2>
+				</section>
+
+				<section data-background="#bb00bb">
+					<h2>data-background: #bb00bb</h2>
+				</section>
+
+				<section data-background-color="lightblue">
+					<h2>data-background: lightblue</h2>
+				</section>
+
+				<section>
+					<section data-background="#ff0000">
+						<h2>data-background: #ff0000</h2>
+					</section>
+					<section data-background="rgba(0, 0, 0, 0.2)">
+						<h2>data-background: rgba(0, 0, 0, 0.2)</h2>
+					</section>
+					<section data-background="salmon">
+						<h2>data-background: salmon</h2>
+					</section>
+				</section>
+
+				<section data-background="rgba(0, 100, 100, 0.2)">
+					<section>
+						<h2>Background applied to stack</h2>
+					</section>
+					<section>
+						<h2>Background applied to stack</h2>
+					</section>
+					<section data-background="rgb(66, 66, 66)">
+						<h2>Background applied to slide inside of stack</h2>
+					</section>
+				</section>
+
+				<section data-background-transition="slide" data-background="assets/image1.png">
+					<h2>Background image</h2>
+				</section>
+
+				<section>
+					<section data-background-transition="slide" data-background="assets/image1.png">
+						<h2>Background image</h2>
+					</section>
+					<section data-background-transition="slide" data-background="assets/image1.png">
+						<h2>Background image</h2>
+					</section>
+				</section>
+
+				<section data-background="assets/image2.png" data-background-size="100px" data-background-repeat="repeat" data-background-color="#111">
+					<h2>Background image</h2>
+					<pre>data-background-size="100px" data-background-repeat="repeat" data-background-color="#111"</pre>
+				</section>
+
+				<section data-background="#888888">
+					<h2>Same background twice (1/2)</h2>
+				</section>
+				<section data-background="#888888">
+					<h2>Same background twice (2/2)</h2>
+				</section>
+
+				<section data-background-video="https://s3.amazonaws.com/static.slid.es/site/homepage/v1/homepage-video-editor.mp4,https://s3.amazonaws.com/static.slid.es/site/homepage/v1/homepage-video-editor.webm">
+					<h2>Video background</h2>
+				</section>
+
+				<section data-background-iframe="https://slides.com/news/make-better-presentations/embed?style=hidden&autoSlide=4000">
+					<h2>Iframe background</h2>
+				</section>
+
+				<section>
+					<section data-background="#417203">
+						<h2>Same background twice vertical (1/2)</h2>
+					</section>
+					<section data-background="#417203">
+						<h2>Same background twice vertical (2/2)</h2>
+					</section>
+				</section>
+
+				<section data-background="#934f4d">
+					<h2>Same background from horizontal to vertical (1/3)</h2>
+				</section>
+				<section>
+					<section data-background="#934f4d">
+						<h2>Same background from horizontal to vertical (2/3)</h2>
+					</section>
+					<section data-background="#934f4d">
+						<h2>Same background from horizontal to vertical (3/3)</h2>
+					</section>
+				</section>
+
+			</div>
+
+		</div>
+
+		<script src="../dist/reveal.js"></script>
+		<script>
+
+			// Full list of configuration options:
+			// https://revealjs.revealjs.com/config/
+			Reveal.initialize({
+				center: true,
+
+				transition: 'linear',
+				// transitionSpeed: 'slow',
+				// backgroundTransition: 'slide'
+			});
+
+		</script>
+
+	</body>
+</html>