Fixes the search box overlapping with content when first shown (#666)

Author: Michael-F-Bryan

src/theme/book.css

@@ -1417,6 +1417,7 @@ mark.fade-out {
   margin-left: auto;
   margin-right: auto;
   max-width: 750px;
+  display: block;
 }
 #searchbar {
   width: 100%;

src/theme/stylus/searchbar.styl

@@ -21,6 +21,7 @@ mark.fade-out {
     margin-left: auto;
     margin-right: auto;
     max-width: $content-max-width;
+    display: block;
 }
 
 #searchbar {
@@ -64,3 +65,4 @@ ul#searchresults {
         font-style: normal;
     }
 }
+