Merge branch 'fix-header-hamburger-positioning' into 'master'

Fixed positioning of hamburger menu on header

Hey guys just noticed the hamburger menu for the top navigation was mis-aligned on 
`gitlab-ce:master` and `gitlab.com`.
I was not able to find an open issue or merge request directly referencing this issue so thought I would add a quick fix.

### Changes

This MR changes the vertical positioning from `top` to vertical margins (Like in bootstrap itself).
 - Also added a minor fix to remove `border-top` from the collapse menu so its the same height as the navigation.
 - finally added an active class to the hamburger toggle so you can see when its open.

This changes an element in `app/views/layouts/header/_default.html.haml` and thus would impact most pages behind login.

## Screenshots

### Before

![before](https://gitlab.com/hanloong/gitlab-ce/uploads/e3d4631dd0420ec0e9048c435a2f734b/before.png)

### After

![after](https://gitlab.com/hanloong/gitlab-ce/uploads/7c93c3ef1b01fbefc39c5a1ed61c2d1b/after.png)

Happy to discuss any changes/suggestions.

Thanks

See merge request !1541

CHANGELOG

@@ -41,6 +41,7 @@ v 8.1.0 (unreleased)
   - Move CI services page to project settings area
   - Add "Quick Submit" behavior to input fields throughout the application. Use
     Cmd+Enter on Mac and Ctrl+Enter on Windows/Linux.
+  - Fix position of hamburger in header for smaller screens (Han Loong Liauw)
 
 v 8.0.4
   - Fix Message-ID header to be RFC 2111-compliant to prevent e-mails being dropped (Stan Hu)

app/assets/javascripts/application.js.coffee

@@ -180,6 +180,7 @@ $ ->
   $('.navbar-toggle').on 'click', ->
     $('.header-content .title').toggle()
     $('.header-content .navbar-collapse').toggle()
+    $('.navbar-toggle').toggleClass('active')
 
   # Show/hide comments on diff
   $("body").on "click", ".js-toggle-diff-comments", (e) ->

app/assets/stylesheets/generic/header.scss

@@ -50,15 +50,17 @@ header {
 
       .navbar-toggle {
         color: #666;
-        margin: 0;
+        margin: 6px 0;
         border-radius: 0;
         position: absolute;
         right: 2px;
-        top: 15px;
 
         &:hover {
           background-color: #EEE;
         }
+        &.active {
+          color: #7f8fa4;
+        }
       }
     }
   }
@@ -87,6 +89,7 @@ header {
 
     .navbar-collapse {
       float: right;
+      border-top: none;
     }
   }