use tooltip plugin to display the name under the avatar

(temporary solution until the proposed solution from the
[pull request](https://github.com/diaspora/diaspora/pull/4149) is
implemented)

app/assets/javascripts/inbox.js

@@ -105,6 +105,11 @@ $(document).ready(function(){
     var self = $(this);
     self.popover('show');
     var popup = self.data('popover').$tip[0];
+
+    // attach tooltips to each avatar showing the name
+    $(popup).find('.avatar').tooltip({ placement: 'bottom' });
+
+    // register handler for the close button
     var close = $(popup).find('.close');
     close.click(function(){
       self.popover('hide');

app/views/conversations/_participants_popover.haml

@@ -1,7 +1,10 @@
 .conversation_participants_popover_content{ :"data-content-conversation-id" => conversation.id }
   .conversation_participants_popover
     - conversation.participants.limit(20).each do |participant|
-      = image_tag(participant.profile.image_url_small, :class => 'avatar', :title => participant.name)
+      = image_tag(participant.profile.image_url_small,
+          :class => 'avatar',
+          :title => participant.name,
+          :data => {:toggle => 'tooltip'})
     - participants_count = conversation.participants.count
     - if participants_count > 20
       %span{ :class => 'participants_left' } And #{participants_count - 20} more