Add remote judge (#16)

* Add feature.

* Add test.

* Add init test.

* Add test.

* Finish the tests, and change the output checking method.

* Add documentation

* Fix test failing in python 3.8.

tests/test_basic.py

@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
 from contextlib import redirect_stdout
 import io
+import unittest
 import os
 import sys
 import unittest