Move admin->runners tab as subnav of overview tab

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/views/admin/dashboard/_head.html.haml

@@ -20,3 +20,7 @@
       = link_to admin_builds_path, title: 'Builds' do
         %span
           Builds
+    = nav_link path: ['runners#index', 'runners#show'] do
+      = link_to admin_runners_path, title: 'Runners' do
+        %span
+          Runners

app/views/admin/runners/index.html.haml

-%p.lead.prepend-top-default
+- @no_container = true
+= render "admin/dashboard/head"
+
+%div{ class: (container_class) }
+
+  %p.prepend-top-default
     %span
       To register a new runner you should enter the following registration token.
       With this token the runner will request a unique runner token and use that for future communication.
+      %br
       Registration token is
       %code{ id: 'runners-token' } #{current_application_settings.runners_registration_token}
 
-.bs-callout.clearfix
+  .bs-callout.clearfix
     .pull-left
       %p
         You can reset runners registration token by pressing a button below.
@@ -16,7 +22,7 @@
           = icon('refresh')
           Reset runners registration token
 
-.bs-callout
+  .bs-callout
     %p
       A 'runner' is a process which runs a build.
       You can setup as many runners as you need.
@@ -37,7 +43,7 @@
           %span.label.label-danger paused
           \- runner will not receive any new builds
 
-.append-bottom-20.clearfix
+  .append-bottom-20.clearfix
     .pull-left
       = form_tag admin_runners_path, id: 'runners-search', class: 'form-inline', method: :get do
         .form-group
@@ -47,9 +53,9 @@
     .pull-right.light
       Runners with last contact less than a minute ago: #{@active_runners_cnt}
 
-%br
+  %br
 
-.table-holder
+  .table-holder
     %table.table
       %thead
         %tr
@@ -64,4 +70,4 @@
 
       - @runners.each do |runner|
         = render "admin/runners/runner", runner: runner
-= paginate @runners
+  = paginate @runners

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

 %ul.nav-links.scrolling-tabs
   .fade-left
-  = nav_link(controller: %w(dashboard admin projects users groups builds), html_options: {class: 'home'}) do
+  = nav_link(controller: %w(dashboard admin projects users groups builds runners), html_options: {class: 'home'}) do
     = link_to admin_root_path, title: 'Overview', class: 'shortcuts-tree' do
       %span
         Overview
@@ -12,10 +12,6 @@
     = link_to admin_deploy_keys_path, title: 'Deploy Keys' do
       %span
         Deploy Keys
-  = nav_link path: ['runners#index', 'runners#show'] do
-    = link_to admin_runners_path, title: 'Runners' do
-      %span
-        Runners
   = nav_link(controller: :broadcast_messages) do
     = link_to admin_broadcast_messages_path, title: 'Messages' do
       %span