Restyle explore page to sidebar layout

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

app/views/explore/projects/trending.html.haml

+.explore-title
+  %h3
+    Explore GitLab
+  %p.lead
+    Discover projects and groups. Share your projects with others
+%hr
 .explore-trending-block
   %p.lead
     %i.fa.fa-comments-o
@@ -7,5 +13,5 @@
     %ul.bordered-list
       = render @trending_projects
 
-  .center
+  .center.append-bottom-20
     = link_to 'Show all projects', explore_projects_path, class: 'btn btn-primary'

app/views/layouts/explore.html.haml

-- page_title = 'Explore'
+- page_title = 'Explore GitLab'
 !!! 5
 %html{ lang: "en"}
   = render "layouts/head", title: page_title
@@ -8,23 +8,5 @@
       = render "layouts/head_panel", title: link_to(page_title, explore_root_path)
     - else
       = render "layouts/public_head_panel", title: link_to(page_title, explore_root_path)
-    .container.navless-container
-      .content
-        .explore-title
-          %h3
-            Explore GitLab
-          %p.lead
-            Discover projects and groups. Share your projects with others
 
-
-        %ul.nav.nav-tabs
-          = nav_link(path: 'projects#trending') do
-            = link_to 'Trending Projects', explore_root_path
-          = nav_link(path: 'projects#starred') do
-            = link_to 'Most Starred Projects', starred_explore_projects_path
-          = nav_link(path: 'projects#index') do
-            = link_to 'All Projects', explore_projects_path
-          = nav_link(controller: :groups) do
-            = link_to 'All Groups', explore_groups_path
-
-        = yield
+    = render 'layouts/page', sidebar: 'layouts/nav/explore'

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

+%ul.nav.nav-sidebar
+  = nav_link(path: 'projects#trending') do
+    = link_to explore_root_path do
+      %i.fa.fa-comments
+      %span Trending Projects
+  = nav_link(path: 'projects#starred') do
+    = link_to starred_explore_projects_path do
+      %i.fa.fa-star
+      %span Most Starred Projects
+  = nav_link(path: 'projects#index') do
+    = link_to explore_projects_path do
+      %i.fa.fa-bookmark
+      %span All Projects
+  = nav_link(controller: :groups) do
+    = link_to explore_groups_path do
+      %i.fa.fa-group
+      %span All Groups
+