Added support for django 2.1

[bhardwajkonark]

No description provided.

[dwebtech]

Request Method:	POST
http://127.0.0.1:8000/admin/backup/
2.2.1
CommandConnectorError
Error running: mysqldump job_python --quick --host=localhost --port=3306 --user=root [WinError 2] The system cannot find the file specified
E:\DoAnCoSo\DoAnCoSo\python_job\venv\lib\site-packages\dbbackup\db\base.py in run_c

[bhardwajkonark]

@dwebtech Please share the following information:
OS, Python Version, Django Version, Mysql Version.

Do you have MySQL cli tools/ MySql Shell installed?

[denizdogan]

I don't understand this PR, it works perfectly fine on Django 2.1 for me and it looks like you just added unused imports to urls.py?