Merge branch 'ui-fixes' into 'master'

Ui fixes

Fixes the ui bugs described in #925.

Also added the suggestion to keep the header at the top of the page.

Fixes #925

Some before/after screenshots:

- Border doesn't reach bottom on smaller pages
  - [Before](https://gitlab.com/uploads/gitlab-org/gitlab-ce/5096094d94/Screenshot_from_2014-12-27_19_49_24.png)
  - [After](https://gitlab.com/uploads/gitlab-org/gitlab-ce/551c1924e4/Screenshot_from_2014-12-27_19_51_43.png)

- Ability to always scroll 48px (visible by the scrollbar)
  - [Before](https://gitlab.com/uploads/gitlab-org/gitlab-ce/ea591bf7b3/Screenshot_from_2014-12-27_19_53_41.png)
  - [After](https://gitlab.com/uploads/gitlab-org/gitlab-ce/97df62b40d/Screenshot_from_2014-12-27_19_53_17.png)

- Mobile sidebar icons off screen (Visible by the scrollbar on the after picture)
  - [Before](https://gitlab.com/uploads/gitlab-org/gitlab-ce/b6d9a4d076/Screenshot_from_2014-12-27_19_49_05.png)
  - [After](https://gitlab.com/uploads/gitlab-org/gitlab-ce/fc52ac31ba/Screenshot_from_2014-12-27_19_48_16.png)

- Header fixed at top
  - [Before](https://gitlab.com/uploads/gitlab-org/gitlab-ce/5d74dc1ea5/Screenshot_from_2014-12-27_19_59_28.png)
  - [After](https://gitlab.com/uploads/gitlab-org/gitlab-ce/57c4c3ea7d/Screenshot_from_2014-12-27_20_00_05.png)

See merge request !269

app/assets/stylesheets/generic/common.scss

@@ -262,7 +262,7 @@ img.emoji {
 }
 
 .navless-container {
-  margin-top: 20px;
+  margin-top: 68px;
 }
 
 .description-block {

app/assets/stylesheets/sections/header.scss

@@ -8,6 +8,9 @@ header {
     margin-bottom: 0;
     min-height: 40px;
     border: none;
+    position: fixed;
+    top: 0;
+    width: 100%;
 
     .navbar-inner {
       filter: none;

app/assets/stylesheets/sections/sidebar.scss

@@ -12,6 +12,7 @@
   width: 100%;
   padding: 15px;
   background: #FFF;
+  margin-top: 48px;
 }
 
 .nav-sidebar {
@@ -105,10 +106,11 @@
 
   .sidebar-wrapper {
     width: 250px;
-    position: absolute;
+    position: fixed;
     left: 250px;
     height: 100%;
     margin-left: -250px;
+    border-right: 1px solid #EAEAEA;
 
     .nav-sidebar {
       margin-top: 20px;
@@ -120,7 +122,6 @@
 
   .content-wrapper {
     padding: 20px;
-    border-left: 1px solid #EAEAEA;
   }
 }
 
@@ -131,14 +132,16 @@
 
   .sidebar-wrapper {
     width: 52px;
-    position: absolute;
-    left: 50px;
+    position: fixed;
+    top: 0;
+    left: 0;
     height: 100%;
-    margin-left: -50px;
+    border-right: 1px solid #EAEAEA;
+    overflow-x: hidden;
 
     .nav-sidebar {
       margin-top: 20px;
-      position: fixed;
+      position: absolute;
       top: 45px;
       width: 52px;