Resolve "Updating own past feedback sets other tutors assignment to is_done=True"

Closes #155 (closed)

core/migrations/0018_auto_20190814_1324.py

+# Generated by Django 2.1.11 on 2019-08-14 13:24
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('core', '0017_auto_20190604_1631'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='feedbacklabel',
+            name='name',
+            field=models.CharField(max_length=50, unique=True),
+        ),
+    ]