Merge branch 'parallel-diff-alignment' into 'master'

Reduce width of parallel diffs

At 50% width the alignment is off on parallel diffs (see https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3785/diffs and view in Side-by-Side)  
Reducing width lines them up:

<img src="/uploads/5775d35b0e86397abd10db6195a8a54d/Screen_Shot_2016-04-22_at_2.19.21_PM.png" width="400px">

Also shifted comment button over to center it properly:  
<img src="/uploads/c2468e15bb65523464a941001c3d7298/Screen_Shot_2016-04-22_at_2.24.33_PM.png" width="200px">

See merge request !3891

app/assets/stylesheets/pages/diff.scss

@@ -98,7 +98,11 @@
       }
 
       td.line_content.parallel {
-        width: 50%;
+        width: 46%;
+      }
+
+      .add-diff-note {
+        margin-left: -65px;
       }
     }
 
@@ -127,8 +131,13 @@
       margin: 0;
       padding: 0 0.5em;
       border: none;
+
       &.parallel {
         display: table-cell;
+
+        span {
+          word-break: break-all;
+        }
       }
     }