Minor updates

Changed invert to naturalSwipe
Removed invert rule from index.html
Ensured that left/right swipes only work with 1 hand present
modified:   index.html
modified:   plugin/leap/leap.js

index.html

@@ -359,9 +359,6 @@ function linkify( selector ) {
 				progress: true,
 				history: true,
 				center: true,
-				leap: {
-			    invert : true
-			  },
 
 				theme: Reveal.getQueryHash().theme, // available themes are in /css/theme
 				transition: Reveal.getQueryHash().transition || 'default', // default/cube/page/concave/zoom/linear/fade/none