Add JS prefix to user tab classes

I'm not entirely sure if this project uses the `js-` prefix for
classes that are for js purposes only. But as I was working on a
feature, I noticed that these classes were those kind of classes.

app/assets/javascripts/user_tabs.js.coffee

@@ -92,7 +92,7 @@ class @UserTabs
     @setCurrentAction(action)
 
   activateTab: (action) ->
-    @parentEl.find(".nav-links .#{action}-tab a").tab('show')
+    @parentEl.find(".nav-links .js-#{action}-tab a").tab('show')
 
   setTab: (source, action) ->
     return if @loaded[action] is true

app/views/users/show.html.haml

@@ -69,13 +69,13 @@
           = @user.location
 
     %ul.nav-links.center.user-profile-nav
-      %li.activity-tab
+      %li.js-activity-tab
         = link_to user_calendar_activities_path, data: {target: 'div#activity', action: 'activity', toggle: 'tab'} do
           Activity
-      %li.groups-tab
+      %li.js-groups-tab
         = link_to user_groups_path, data: {target: 'div#groups', action: 'groups', toggle: 'tab'} do
           Groups
-      %li.contributed-tab
+      %li.js-contributed-tab
         = link_to user_contributed_projects_path, data: {target: 'div#contributed', action: 'contributed', toggle: 'tab'} do
           Contributed projects
       %li.projects-tab