Add some semantic to our html

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

app/views/dashboard/show.html.haml

 - if @has_authorized_projects
   .dashboard.row
-    .activities.col-md-8
+    %section.activities.col-md-8
       = render 'activities'
-    .side.col-md-4.left.responsive-side
+    %aside.side.col-md-4.left.responsive-side
       = render 'sidebar'
 
   .fixed.sidebar-expand-button.hidden-lg.hidden-md

app/views/groups/show.html.haml

 .dashboard
-  .activities.col-md-8.hidden-sm.hidden-xs
+  %section.activities.col-md-8.hidden-sm.hidden-xs
     - if current_user
       = render "events/event_last_push", event: @last_push
       = link_to dashboard_path, class: 'btn btn-tiny' do
@@ -16,7 +16,7 @@
     - else
       .nothing-here-block Project activity will be displayed here
     = spinner
-  .side.col-md-4
+  %aside.side.col-md-4
     .light-well.append-bottom-20
       = image_tag group_icon(@group.path), class: "avatar s90"
       .clearfix.light

app/views/projects/blob/_blob.html.haml

@@ -20,7 +20,7 @@
   = render blob_commit, project: @project
 
 %div#tree-content-holder.tree-content-holder
-  .file-holder
+  %article.file-holder
     .file-title.clearfix
       %i.icon-file
       %span.file_name

app/views/projects/show.html.haml

 = render "home_panel"
 
 .row
-  .col-md-9
+  %section.col-md-9
     = render "events/event_last_push", event: @last_push
     = render 'shared/event_filter'
     .content_list
     = spinner
-  .col-md-3.project-side.hidden-sm.hidden-xs
+  %aside.col-md-3.project-side.hidden-sm.hidden-xs
     .clearfix
       - if @project.archived?
         .alert.alert-warning

app/views/projects/tree/_readme.html.haml

-.readme-holder#README
+%article.readme-holder#README
   %h4.readme-file-title
     %i.icon-file
     = readme.name