fix header nav font size and hr

vocodes/src/App.scss

@@ -113,7 +113,6 @@ nav {
     text-decoration: none;
     color: $light-text-color;
     padding: 0 10px;
-    font-size: 1.3em;
     cursor: pointer;
   }
   a:after {
@@ -124,6 +123,10 @@ nav {
   a:active {
     background-color: #bfdff5;
   }
+
+  hr {
+    margin: 5px 0 15px 0;
+  }
 }
 
 .button-group {