修改 submission 的 model，增加是否分享字段。已经 migrate

submission/migrations/0006_submission_shared.py

@@ -0,0 +1,19 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models, migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('submission', '0005_submission_contest_id'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='submission',
+            name='shared',
+            field=models.BooleanField(default=False),
+        ),
+    ]