Use ajax form for artist commentary

This prevents the parameters (eg. ?tags=whatever) from being eaten on
submit.

app/views/artist_commentaries/_form.html.erb

@@ -1,6 +1,6 @@
 <p>If the artist of this image posted some interesting additional information about this work, you can copy it here.</p>
 
-<%= form_tag(create_or_update_artist_commentaries_path, :class => "simple_form", :method => :put) do %>
+<%= form_tag(create_or_update_artist_commentaries_path(:format => :js), :remote => true, :class => "simple_form", :method => :put) do %>
   <div class="input">
     <%= hidden_field :artist_commentary, :post_id, :value => @post.id %>
 

app/views/artist_commentaries/create_or_update.js.erb

@@ -0,0 +1 @@
+location.reload();