Update to last reveal.js 4.2.1 (#148)

diff --git a/DESCRIPTION b/DESCRIPTION
index 2593d42..fb0a695 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Type: Package
 Package: revealjs
 Title: R Markdown Format for 'reveal.js' Presentations
-Version: 0.9.1.9006
+Version: 0.9.1.9007
 Date: 2017-03-13
 Authors@R: 
     c(person(given = "Hakim",