No margin-bottom for last p inside li tags (#262)

Fixes #241.

assets/css/screen.css

@@ -295,6 +295,10 @@ li li {
     margin: 0;
 }
 
+li > p:last-of-type {
+    margin-bottom: 0;
+}
+
 hr {
     display: block;
     height: 1px;