Fix broken tag autocomplete on multiple pages.

Mark all tag <input>s with a `data-autocomplete` attribute, instead of
hardcoding a list of html IDs to autocomplete in javascript.

This way should be less error prone. It fixes autocomplete in several places:

* Autocomplete for the search box on /posts didn't work in the
  responsive layout. This was because /posts has two search boxes that
  both have the id `tags`: one in the normal sidebar, and one in the
  responsive tag list. $("#tags") only initialized autocomplete on the
  first one.

* Autocomplete didn't work on the aliases or implications pages. This
  was due to selecting the wrong html ids.

app/views/moderator/bulk_reverts/new.html.erb

@@ -22,13 +22,13 @@
 
       <div class="input" id="added-tags-input">
         <label>Added Tags</label>
-        <%= text_field :constraints, :added_tags, :value => @constraints[:added_tags] %>
+        <%= text_field :constraints, :added_tags, :value => @constraints[:added_tags], :data => { :autocomplete => "tag" } %>
         <p class="hint">You must specify a user to add tags</p>
       </div>
 
       <div class="input" id="removed-tags-input">
         <label>Removed Tags</label>
-        <%= text_field :constraints, :removed_tags, :value => @constraints[:removed_tags] %>
+        <%= text_field :constraints, :removed_tags, :value => @constraints[:removed_tags], :data => { :autocomplete => "tag" } %>
         <p class="hint">You must specify a user to add tags</p>
       </div>
 
@@ -96,4 +96,4 @@
       });
     });
   <% end %>
-<% end %>
+<% end %>