Change header color in network page

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/assets/stylesheets/sections/graph.scss

 .project-network {
-  border: 1px solid #aaa;
-  padding: 1px;
+  border: 1px solid #CCC;
 
   .tip {
     color: #888;
     font-size: 14px;
     padding: 10px;
     border-bottom: 1px solid #bbb;
-    @include bg-gray-gradient;
+    background: #EEE;
   }
 
   .network-graph {
-    background: #f1f1f1;
+    background: #FFF;
     height: 500px;
     overflow-y: scroll;
     overflow-x: hidden;