Ensure gists display well at all device widths

src/css/app.css

@@ -11,6 +11,12 @@ p.meta {
   width: 55%;
 }
 
+@media (max-width: 760px) {
+  .gist {
+    width: 100%;
+  }
+}
+
 figure iframe {
   max-width: 100%;
 }