Add tooltip icon to retried builds

app/assets/stylesheets/pages/builds.scss

@@ -195,7 +195,7 @@
     .build-job {
       position: relative;
 
-      .fa {
+      .fa-check {
         position: absolute;
         left: 15px;
         top: 20px;

app/views/projects/builds/_sidebar.html.haml

@@ -135,11 +135,5 @@
                 = build.name
               - else
                 = build.id
-
-      - if @build.retried?
-        %li.active
-          %a
-            Build ##{@build.id}
-            ·
-            %i.fa.fa-warning
-            This build was retried.
+            - if @build.retried?
+              %i.fa.fa-warning.has-tooltip{data: { container: 'body', placement: 'bottom' }, title: 'This build was retried'}