Add migration for enforced unique email

opentech/apply/users/migrations/0004_enforce_unique_email.py

+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.8 on 2018-01-25 10:16
+from __future__ import unicode_literals
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('users', '0003_user_full_name'),
+    ]
+
+    operations = [
+        migrations.AlterModelOptions(
+            name='user',
+            options={},
+        ),
+        migrations.AlterUniqueTogether(
+            name='user',
+            unique_together=set([('email',)]),
+        ),
+    ]