Override ipython css for .fade

Fixes  #188

nbconvert/templates/reveal.tpl

@@ -55,6 +55,9 b' box-shadow: 0 0 10px rgba(0, 0, 0, 0);'
 .reveal .slides {
 text-align: left;
 }
+.reveal.fade {
+opacity: 1;
+}
 div.input_area {
 padding: 0.06em;
 }