Merge pull request #207 from edufresne/master

Truncate zip file before re-writing it for  replace_media with file-like objects

docxtpl/__init__.py

@@ -463,6 +463,8 @@ class DocxTemplate(object):
                 DocxTemplate(docx_file).save(tmp_file)
                 tmp_file.seek(0)
                 docx_file.seek(0)
+                docx_file.truncate()
+                docx_file.seek(0)
 
             else:
                 tmp_file = '%s_docxtpl_before_replace_medias' % docx_file