Don't initialize Tree History unless tree-slider is present

This was breaking breadcrumb links on non-Tree pages

app/assets/javascripts/tree.js.coffee

@@ -17,23 +17,21 @@ $ ->
       "ajax:beforeSend": -> $('.tree_progress').addClass("loading")
       "ajax:complete":   -> $('.tree_progress').removeClass("loading")
 
-# Maintain forward/back history while browsing the file tree
-
-((window) ->
-  History = window.History
-  $ = window.jQuery
-  document = window.document
-
-  # Check to see if History.js is enabled for our Browser
-  unless History.enabled
-    return false
-
-  $ ->
-    $('#tree-slider .tree-item-file-name a, .breadcrumb li > a').live 'click', (e) ->
-      History.pushState(null, null, $(@).attr('href'))
-      return false
-
-    History.Adapter.bind window, 'statechange', ->
-      state = History.getState()
-      window.ajaxGet(state.url)
-)(window)
+    # Maintain forward/back history while browsing the file tree
+    ((window) ->
+      History = window.History
+      $ = window.jQuery
+      document = window.document
+
+      # Check to see if History.js is enabled for our Browser
+      unless History.enabled
+        return false
+
+      $('#tree-slider .tree-item-file-name a, .breadcrumb li > a').live 'click', (e) ->
+        History.pushState(null, null, $(@).attr('href'))
+        return false
+
+      History.Adapter.bind window, 'statechange', ->
+        state = History.getState()
+        window.ajaxGet(state.url)
+    )(window)