make 'o' active bookmarks as well

hitting 'o' or clicking a bookmark will now make that bookmark to the
new tree root, in the same way that :BookmarkToRoot does

plugin/NERD_tree.vim

@@ -1990,6 +1990,17 @@ function! s:GetPath(ln)
     return toReturn
 endfunction
 
+"FUNCTION: s:GetSelectedBookmark() {{{2
+"Returns the current node if it is a dir node, or else returns the current
+"nodes parent
+function! s:GetSelectedBookmark()
+    let line = getline(".")
+    let name = substitute(line, '^>\(.\{-}\) \[.*\]$', '\1', '')
+    if name != line
+        return name
+    endif
+endfunction
+
 "FUNCTION: s:GetSelectedDir() {{{2
 "Returns the current node if it is a dir node, or else returns the current
 "nodes parent
@@ -2572,12 +2583,9 @@ function! s:ActivateNode()
     if getline(".") == s:tree_up_dir_line
         return s:UpDir(0)
     endif
-    let treenode = s:GetSelectedNode()
-    if treenode == {}
-        call s:EchoWarning("cannot open selected entry")
-        return
-    endif
 
+    let treenode = s:GetSelectedNode()
+    if treenode != {}
         if treenode.path.isDirectory
             call treenode.ToggleOpen()
             call s:RenderView()
@@ -2588,6 +2596,12 @@ function! s:ActivateNode()
                 call s:CloseTree()
             endif
         endif
+    else
+        let bookmark = s:GetSelectedBookmark()
+        if bookmark != ""
+            call s:BookmarkToRoot(bookmark)
+        endif
+    endif
 endfunction
 
 "FUNCTION: s:BindMappings() {{{2