fix tagger docs, if extension is blank/None, don't add an extension

hyde/ext/plugins/meta.py

@@ -295,7 +295,7 @@ class TaggerPlugin(Plugin):
                template: tagged_posts.j2
                source: blog
                target: blog/tags
-               archive_extension: html
+               extension: html
     """
 
     def __init__(self, site):
@@ -423,7 +423,11 @@ extends: false
                 "meta": meta_text
             }
             text = archive_text % tag_data
-            archive_file = File(target.child("%s.%s" % (tagname, extension)))
+            if extension:
+                fname = "%s.%s" % (tagname, extension)
+            else:
+                fname = tagname
+            archive_file = File(target.child(fname))
             archive_file.delete()
             archive_file.write(text.strip())
             self.site.content.add_resource(archive_file)