Merge branch 'explore-markdown' into 'master'

Apply markdown filter for project descriptions on explore view

When you open the explore page, then the project descriptions are not rendered correctly (e.g., https://gitlab.com/search?search=tortoisegit).

See merge request !1098

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

@@ -9,8 +9,8 @@
 
   .project-info
     - if project.description.present?
-      %p.project-description.str-truncated
-        = project.description
+      .project-description.str-truncated
+        = markdown(project.description, pipeline: :description)
 
     .repo-info
       - unless project.empty_repo?