responds with ajax to comment creation [#47]

app/views/comments/_form.html.erb

@@ -1,7 +1,7 @@
 <%= link_to comment_link_text(parent), "", class: "js-add-comment-link", data: {'id': dom_id(parent)} %>
 
 <div id="js-comment-form-<%= dom_id(parent) %>" style="display:none">
-  <%= form_for [@debate, Comment.new] do |f| %>
+  <%= form_for [@debate, Comment.new], remote: true do |f| %>
     <%= f.text_area :body %>
     <%= f.hidden_field :commentable_type, value: parent.class %>
     <%= f.hidden_field :commentable_id, value: parent.id %>

app/views/comments/create.js.erb

@@ -0,0 +1,4 @@
+var form = "#js-comment-form-<%= dom_id(@parent) %>"
+$(form + " #comment_body").val('');
+$(form).hide();
+$("<%= j(render @comment) %>").insertAfter($(form));