Avoid document plugin problem on XHTML documents

jQuery will choke if the img tag isn't closed.

Author: tilgovi

src/plugin/document.coffee

@@ -143,7 +143,7 @@ class Annotator.Plugin.Document extends Annotator.Plugin
   # hack to get a absolute url from a possibly relative one
 
   _absoluteUrl: (url) ->
-    img = $("<img src='#{ url }'>")
+    img = $("<img src='#{ url }'></img>")
     url = img.prop('src')
     img.prop('src', null)
     return url