Add missing migrations

petitions/migrations/0003_auto_20171004_2139.py

+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.4 on 2017-10-04 19:39
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('petitions', '0002_auto_20171004_2107'),
+    ]
+
+    operations = [
+        migrations.AlterModelOptions(
+            name='petitionsignatory',
+            options={'ordering': ['last_name', 'country_of_employment', 'affiliation'], 'verbose_name_plural': 'petition signatories'},
+        ),
+        migrations.AlterField(
+            model_name='petitionsignatory',
+            name='petition',
+            field=models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='petition_signatories', to='petitions.Petition'),
+        ),
+        migrations.AlterField(
+            model_name='petitionsignatory',
+            name='signatory',
+            field=models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.CASCADE, related_name='petition_signatories', to='scipost.Contributor'),
+        ),
+    ]