Make issue buttons look more consistent with MRs

app/views/issues/show.html.haml

@@ -8,11 +8,11 @@
   %span.right
     - if can?(current_user, :admin_project, @project) || @issue.author == current_user
       - if @issue.closed
-        = link_to 'Reopen', project_issue_path(@project, @issue, issue: {closed: false }, status_only: true), method: :put,  class: "btn small"
+        = link_to 'Reopen', project_issue_path(@project, @issue, issue: {closed: false }, status_only: true), method: :put,  class: "btn grouped success"
       - else
-        = link_to 'Close', project_issue_path(@project, @issue, issue: {closed: true }, status_only: true), method: :put, class: "btn small", title: "Close Issue"
+        = link_to 'Close', project_issue_path(@project, @issue, issue: {closed: true }, status_only: true), method: :put, class: "btn grouped danger", title: "Close Issue"
     - if can?(current_user, :admin_project, @project) || @issue.author == current_user
-      = link_to edit_project_issue_path(@project, @issue), class: "btn small" do
+      = link_to edit_project_issue_path(@project, @issue), class: "btn grouped" do
         %i.icon-edit
         Edit