Update to last reveal.js 4.2.1 (#148)

diff --git a/inst/reveal.js-4.2.1/js/controllers/location.js b/inst/reveal.js-4.2.1/js/controllers/location.js
new file mode 100644
index 0000000..ec86e65
--- /dev/null
+++ b/inst/reveal.js-4.2.1/js/controllers/location.js
@@ -0,0 +1,219 @@
+/**
+ * Reads and writes the URL based on reveal.js' current state.
+ */
+export default class Location {
+
+	constructor( Reveal ) {
+
+		this.Reveal = Reveal;
+
+		// Delays updates to the URL due to a Chrome thumbnailer bug
+		this.writeURLTimeout = 0;
+
+		this.onWindowHashChange = this.onWindowHashChange.bind( this );
+
+	}
+
+	bind() {
+
+		window.addEventListener( 'hashchange', this.onWindowHashChange, false );
+
+	}
+
+	unbind() {
+
+		window.removeEventListener( 'hashchange', this.onWindowHashChange, false );
+
+	}
+
+	/**
+	 * Returns the slide indices for the given hash link.
+	 *
+	 * @param {string} [hash] the hash string that we want to
+	 * find the indices for
+	 *
+	 * @returns slide indices or null
+	 */
+	getIndicesFromHash( hash=window.location.hash ) {
+
+		// Attempt to parse the hash as either an index or name
+		let name = hash.replace( /^#\/?/, '' );
+		let bits = name.split( '/' );
+
+		// If the first bit is not fully numeric and there is a name we
+		// can assume that this is a named link
+		if( !/^[0-9]*$/.test( bits[0] ) && name.length ) {
+			let element;
+
+			let f;
+
+			// Parse named links with fragments (#/named-link/2)
+			if( /\/[-\d]+$/g.test( name ) ) {
+				f = parseInt( name.split( '/' ).pop(), 10 );
+				f = isNaN(f) ? undefined : f;
+				name = name.split( '/' ).shift();
+			}
+
+			// Ensure the named link is a valid HTML ID attribute
+			try {
+				element = document.getElementById( decodeURIComponent( name ) );
+			}
+			catch ( error ) { }
+
+			if( element ) {
+				return { ...this.Reveal.getIndices( element ), f };
+			}
+		}
+		else {
+			const config = this.Reveal.getConfig();
+			let hashIndexBase = config.hashOneBasedIndex ? 1 : 0;
+
+			// Read the index components of the hash
+			let h = ( parseInt( bits[0], 10 ) - hashIndexBase ) || 0,
+				v = ( parseInt( bits[1], 10 ) - hashIndexBase ) || 0,
+				f;
+
+			if( config.fragmentInURL ) {
+				f = parseInt( bits[2], 10 );
+				if( isNaN( f ) ) {
+					f = undefined;
+				}
+			}
+
+			return { h, v, f };
+		}
+
+		// The hash couldn't be parsed or no matching named link was found
+		return null
+
+	}
+
+	/**
+	 * Reads the current URL (hash) and navigates accordingly.
+	 */
+	readURL() {
+
+		const currentIndices = this.Reveal.getIndices();
+		const newIndices = this.getIndicesFromHash();
+
+		if( newIndices ) {
+			if( ( newIndices.h !== currentIndices.h || newIndices.v !== currentIndices.v || newIndices.f !== undefined ) ) {
+					this.Reveal.slide( newIndices.h, newIndices.v, newIndices.f );
+			}
+		}
+		// If no new indices are available, we're trying to navigate to
+		// a slide hash that does not exist
+		else {
+			this.Reveal.slide( currentIndices.h || 0, currentIndices.v || 0 );
+		}
+
+	}
+
+	/**
+	 * Updates the page URL (hash) to reflect the current
+	 * state.
+	 *
+	 * @param {number} delay The time in ms to wait before
+	 * writing the hash
+	 */
+	writeURL( delay ) {
+
+		let config = this.Reveal.getConfig();
+		let currentSlide = this.Reveal.getCurrentSlide();
+
+		// Make sure there's never more than one timeout running
+		clearTimeout( this.writeURLTimeout );
+
+		// If a delay is specified, timeout this call
+		if( typeof delay === 'number' ) {
+			this.writeURLTimeout = setTimeout( this.writeURL, delay );
+		}
+		else if( currentSlide ) {
+
+			let hash = this.getHash();
+
+			// If we're configured to push to history OR the history
+			// API is not avaialble.
+			if( config.history ) {
+				window.location.hash = hash;
+			}
+			// If we're configured to reflect the current slide in the
+			// URL without pushing to history.
+			else if( config.hash ) {
+				// If the hash is empty, don't add it to the URL
+				if( hash === '/' ) {
+					window.history.replaceState( null, null, window.location.pathname + window.location.search );
+				}
+				else {
+					window.history.replaceState( null, null, '#' + hash );
+				}
+			}
+			// UPDATE: The below nuking of all hash changes breaks
+			// anchors on pages where reveal.js is running. Removed
+			// in 4.0. Why was it here in the first place? ¯\_(ツ)_/¯
+			//
+			// If history and hash are both disabled, a hash may still
+			// be added to the URL by clicking on a href with a hash
+			// target. Counter this by always removing the hash.
+			// else {
+			// 	window.history.replaceState( null, null, window.location.pathname + window.location.search );
+			// }
+
+		}
+
+	}
+
+	/**
+	 * Return a hash URL that will resolve to the given slide location.
+	 *
+	 * @param {HTMLElement} [slide=currentSlide] The slide to link to
+	 */
+	getHash( slide ) {
+
+		let url = '/';
+
+		// Attempt to create a named link based on the slide's ID
+		let s = slide || this.Reveal.getCurrentSlide();
+		let id = s ? s.getAttribute( 'id' ) : null;
+		if( id ) {
+			id = encodeURIComponent( id );
+		}
+
+		let index = this.Reveal.getIndices( slide );
+		if( !this.Reveal.getConfig().fragmentInURL ) {
+			index.f = undefined;
+		}
+
+		// If the current slide has an ID, use that as a named link,
+		// but we don't support named links with a fragment index
+		if( typeof id === 'string' && id.length ) {
+			url = '/' + id;
+
+			// If there is also a fragment, append that at the end
+			// of the named link, like: #/named-link/2
+			if( index.f >= 0 ) url += '/' + index.f;
+		}
+		// Otherwise use the /h/v index
+		else {
+			let hashIndexBase = this.Reveal.getConfig().hashOneBasedIndex ? 1 : 0;
+			if( index.h > 0 || index.v > 0 || index.f >= 0 ) url += index.h + hashIndexBase;
+			if( index.v > 0 || index.f >= 0 ) url += '/' + (index.v + hashIndexBase );
+			if( index.f >= 0 ) url += '/' + index.f;
+		}
+
+		return url;
+
+	}
+
+	/**
+	 * Handler for the window level 'hashchange' event.
+	 *
+	 * @param {object} [event]
+	 */
+	onWindowHashChange( event ) {
+
+		this.readURL();
+
+	}
+
+}
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