Just fixing a css property.

This fix a css bug when you use larger fonts.

nbconvert/templates/reveal.tpl

@@ -41,7 +41,7 b' overflow-y: auto;'
 overflow-x: hidden;
 }
 .reveal pre {
-width: 98%;
+width: 95%;
 padding: 0.4em;
 margin: 0px;
 font-family: monospace, sans-serif;