Add .random-books class to random books div (#757)

Assist caliBlur in targeting this element

cps/templates/index.html

@@ -1,7 +1,7 @@
 {% extends "layout.html" %}
 {% block body %}
 {% if g.user.show_detail_random() %}
-<div class="discover">
+<div class="discover random-books">
   <h2 class="random-books">{{_('Discover (Random Books)')}}</h2>
   <div class="row">