Fix some errors in :command-complete-custom. Fix some help tags not appearing.

pentadactyl/locale/en-US/intro.xml

@@ -15,7 +15,7 @@
     and finger feel should be familiar to Vim users.
 </p>
 
-<ol replace="topics-list">
+<ol tag="topics-list" replace="topics-list">
     <li>
         <link topic="tutorial">Quick-start tutorial</link>:
         A quick-start tutorial for new users.
@@ -116,7 +116,7 @@
     </li>
 </ol>
 
-<ul replace="features-list">
+<ul tag="features-list" replace="features-list">
     <li>Vim-like keybindings (<k>h</k>, <k>j</k>, <k>gg</k>, <k>ZZ</k>, <k name="C-f"/>, etc.)</li>
     <li>Ex commands (<ex>:quit</ex>, <ex>:open www.foo.com</ex>, …)</li>
     <li>Tab completion for all commands, highly configurable via <o>wildmode</o>, <o>autocomplete</o>, ...</li>