make API navbar relative position like rest of site (#317)

Author: jenweber

app/styles/app.scss

@@ -12,14 +12,10 @@ body {
   width: 100%;
 }
 
-.header {
-  z-index: 2;
-}
-@include media($medium-large-screen-up) {
+@include media($large-screen-up) {
   .header {
     top: 0;
     width: 100%;
-    position: fixed;
   }
 
   main.container {
@@ -29,7 +25,6 @@ body {
   main.container .content {
     position: relative;
     margin-right: 0;
-    margin-top: $top-spacing;
     margin-bottom: 0;
     overflow:auto;
     padding: $base-spacing;

app/styles/components/_sidebar.scss

@@ -5,10 +5,6 @@
   z-index: 1;
   padding: $small-spacing 0;
 
-  @include media($medium-screen-up) {
-    margin-top: 11em;
-  }
-
   @include media($large-screen-up) {
     // fixed sidebar, full height
     @include span-columns(3.5);
@@ -17,7 +13,6 @@
     border-bottom: 0;
     border-right: $base-border;
     padding: $small-spacing $base-spacing $base-spacing * 1.5;
-    margin-top: 5em;
 
     &::before {
       @include position(absolute, 0 0 0 -100vw);