Improve tooltips on admin menu

app/views/layouts/nav/_admin.html.haml

 %ul.nav.nav-sidebar
   = nav_link(controller: :dashboard, html_options: {class: 'home'}) do
-    = link_to admin_root_path, title: "Stats" do
+    = link_to admin_root_path, title: 'Overview' do
       = icon('dashboard fw')
       %span
         Overview
@@ -25,13 +25,13 @@
       %span
         Deploy Keys
   = nav_link path: ['runners#index', 'runners#show'] do
-    = link_to admin_runners_path do
+    = link_to admin_runners_path, title: 'Runners' do
       = icon('cog fw')
       %span
         Runners
         %span.count= number_with_delimiter(Ci::Runner.count(:all))
   = nav_link path: 'builds#index' do
-    = link_to admin_builds_path do
+    = link_to admin_builds_path, title: 'Builds' do
       = icon('link fw')
       %span
         Builds