Tests: add test project

* manage.py file at the root of the project
* targetting the project located at tests/test_project/settings.py

That allows testing the linter through just calling it on the project itself.
Using the new method coming soon: `python manage.py lintmigrations`

tests/test_project/app_drop_column/admin.py

@@ -0,0 +1,6 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.contrib import admin
+
+# Register your models here.

tests/test_project/app_drop_column/apps.py

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+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.apps import AppConfig
+
+
+class AppDropColumnConfig(AppConfig):
+    name = "tests.test_project.app_drop_column"

tests/test_project/app_drop_column/migrations/0001_initial.py

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+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.18 on 2019-04-14 14:59
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = []
+
+    operations = [
+        migrations.CreateModel(
+            name="A",
+            fields=[
+                (
+                    "id",
+                    models.AutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("field_a", models.IntegerField()),
+                ("field_b", models.CharField(max_length=10)),
+            ],
+        )
+    ]

tests/test_project/app_drop_column/migrations/0002_remove_a_field_b.py

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+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.18 on 2019-04-14 14:59
+from __future__ import unicode_literals
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [("app_drop_column", "0001_initial")]
+
+    operations = [migrations.RemoveField(model_name="a", name="field_b")]

tests/test_project/app_drop_column/models.py

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+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models
+
+
+class A(models.Model):
+    field_a = models.IntegerField()

tests/test_project/app_drop_column/tests.py

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+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.test import TestCase
+
+# Create your tests here.

tests/test_project/app_drop_column/views.py

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+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.shortcuts import render
+
+# Create your views here.