fixed shelf clipping bug on large screen sizes (#1089)

changed it to be a percentage over 1500px screen width

Author: JeremyRudman

sass/main.scss

@@ -250,7 +250,7 @@ nav {
     #shelf {
         position: absolute;
         width: 100%;
-        height: 250px;
+        height: 25%;
         left: 0;
         right: 0;
         bottom: -20px; // Crop SVG slightly