后端增加题目 io mode 相关逻辑

problem/migrations/0013_problem_io_mode.py

@@ -0,0 +1,20 @@
+# Generated by Django 2.1.7 on 2019-03-12 07:13
+
+import django.contrib.postgres.fields.jsonb
+from django.db import migrations
+import problem.models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('problem', '0012_auto_20180501_0436'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='problem',
+            name='io_mode',
+            field=django.contrib.postgres.fields.jsonb.JSONField(default=problem.models._default_io_mode),
+        ),
+    ]