Fix investment form padding in Internet Explorer

It looks like Internet Explorer wasn't applying the padding to the
<main> element because it considered it an inline element.

app/assets/stylesheets/layout.scss

@@ -64,6 +64,10 @@ body {
   }
 }
 
+main {
+  display: block;
+}
+
 h1,
 h2,
 h3,