Fix dictionary export with Django 1.8

The storage.savefile() does also close the output file, causing Django
1.8 to close the transaction preliminary leading to various strange
problems.
Signed-off-by: Michal Čihař <michal@cihar.com>

weblate/trans/views/dictionary.py

@@ -231,7 +231,7 @@ def download_dictionary_ttkit(export_format, prj, lang, words):
         store.addunit(unit)
 
     # Save to response
-    store.savefile(response)
+    response.write(str(store))
 
     return response