comments.js: fix forms flickering on page load.

Mark the edit form, new comment form, and unvote links as hidden in
html, instead of showing them by default then hiding them later in
Javascript. This eliminates flickering on page load.

app/views/comments/_form.html.erb

@@ -1,6 +1,6 @@
 <%= error_messages_for :comment %>
 
-<%= simple_form_for(comment, :html => {:class => "edit_comment"}) do |f| %>
+<%= simple_form_for(comment, :html => {:style => ("display: none;" if local_assigns[:hidden]), :class => "edit_comment"}) do |f| %>
   <%= f.hidden_field :post_id %>
   <%= dtext_field "comment", "body", :classes => "autocomplete-mentions", :value => comment.body, :input_id => "comment_body_for_#{comment.id}", :preview_id => "dtext-preview-for-#{comment.id}" %>
   <%= f.button :submit, "Submit" %>