Convert warnings to use bootstrap alerts

The new note is guidance, rather than a warning, so it gets the info
background

app/views/browse/new_note.html.erb

@@ -6,7 +6,7 @@
 </h2>
 
 <div class="note browse-section">
-  <p class="warning"><%= t("javascripts.notes.new.intro") %></p>
+  <p class="alert alert-info"><%= t("javascripts.notes.new.intro") %></p>
   <form action="#">
     <input type="hidden" name="lon">
     <input type="hidden" name="lat">

app/views/browse/note.html.erb

@@ -12,15 +12,14 @@
   </div>
 
   <div class="details" data-coordinates="<%= @note.lat %>,<%= @note.lon %>" data-status="<%= @note.status %>">
-    <%= note_event("opened", @note.created_at, @note.author) %>
+    <p><%= note_event("opened", @note.created_at, @note.author) %></p>
     <% if @note.status == "closed" %>
-      <br />
+      <p><%= note_event(@note.status, @note.closed_at, @note.all_comments.last.author) %></p>
-      <%= note_event(@note.status, @note.closed_at, @note.all_comments.last.author) %>
     <% end %>
   </div>
 
   <% if @note_comments.find { |comment| comment.author.nil? } -%>
-    <p class='warning'><%= t "javascripts.notes.show.anonymous_warning" %></p>
+    <p class='alert alert-warning'><%= t "javascripts.notes.show.anonymous_warning" %></p>
   <% end -%>
 
   <% if current_user && current_user != @note.author %>

app/views/site/export.html.erb

@@ -24,7 +24,7 @@
   <p><%= t ".export_details_html" %></p>
 
   <div id="export_osm_too_large">
-    <p class="warning">
+    <p class="alert alert-warning">
       <%= t ".too_large.body" %>
     </p>
   </div>