add erb mode

demo/kitchen-sink/docs/html_ruby.erb

@@ -0,0 +1,25 @@
+<h1>Listing Books</h1>
+ 
+<table>
+  <tr>
+    <th>Title</th>
+    <th>Summary</th>
+    <th></th>
+    <th></th>
+    <th></th>
+  </tr>
+ 
+<% @books.each do |book| %>
+  <tr>
+    <td><%= book.title %></td>
+    <td><%= book.content %></td>
+    <td><%= link_to 'Show', book %></td>
+    <td><%= link_to 'Edit', edit_book_path(book) %></td>
+    <td><%= link_to 'Remove', book, :confirm => 'Are you sure?', :method => :delete %></td>
+  </tr>
+<% end %>
+</table>
+ 
+<br />
+ 
+<%= link_to 'New book', new_book_path %>