Make post body h2's smaller on index pages

Previously, <h2>s in a post were the exact same size as post titles on
index pages (blog index, tag listing). This fixes that by reducing the
font-size of body h2's. Closes #82.

less/core.less

@@ -604,6 +604,9 @@ body#collection article, body#subpage article {
 	padding-top: 0;
 	padding-bottom: 0;
 	.book {
+		h2 {
+			font-size: 1.4em;
+		}
 		a.hidden.action {
 			 color: #666;
 			 float: right;