Remove 'from __future__ import unicode_literals' statements (issue wagtail#518)

Fixes wagtail#518

Author: input

bakerydemo/base/migrations/0001_initial.py

@@ -1,7 +1,5 @@
 # -*- coding: utf-8 -*-
 # Generated by Django 1.10.5 on 2017-03-15 07:16
-from __future__ import unicode_literals
-
 from django.db import migrations, models
 import django.db.models.deletion
 import modelcluster.fields

bakerydemo/base/migrations/0002_auto_20170329_0055.py

@@ -1,7 +1,5 @@
 # -*- coding: utf-8 -*-
 # Generated by Django 1.10.5 on 2017-03-29 00:55
-from __future__ import unicode_literals
-
 from django.db import migrations
 import wagtail.blocks
 import wagtail.fields

bakerydemo/base/migrations/0003_auto_20170823_1127.py

@@ -1,7 +1,5 @@
 # -*- coding: utf-8 -*-
 # Generated by Django 1.11.3 on 2017-08-23 11:27
-from __future__ import unicode_literals
-
 from django.db import migrations, models
 
 

bakerydemo/base/models.py

@@ -1,5 +1,3 @@
-from __future__ import unicode_literals
-
 from django.conf import settings
 from django.contrib.contenttypes.fields import GenericRelation
 from django.db import models

bakerydemo/blog/migrations/0001_initial.py

@@ -1,7 +1,5 @@
 # -*- coding: utf-8 -*-
 # Generated by Django 1.10.5 on 2017-03-15 07:16
-from __future__ import unicode_literals
-
 from django.db import migrations, models
 import django.db.models.deletion
 import modelcluster.contrib.taggit

bakerydemo/blog/migrations/0002_remove_blogindexpage_body.py

@@ -1,7 +1,5 @@
 # -*- coding: utf-8 -*-
 # Generated by Django 1.10.5 on 2017-03-26 22:25
-from __future__ import unicode_literals
-
 from django.db import migrations
 
 

bakerydemo/blog/migrations/0003_auto_20170329_0055.py

@@ -1,7 +1,5 @@
 # -*- coding: utf-8 -*-
 # Generated by Django 1.10.5 on 2017-03-29 00:55
-from __future__ import unicode_literals
-
 from django.db import migrations
 import wagtail.blocks
 import wagtail.fields

bakerydemo/blog/models.py

@@ -1,5 +1,3 @@
-from __future__ import unicode_literals
-
 from django.contrib import messages
 from django.db import models
 from django.shortcuts import redirect, render

bakerydemo/breads/migrations/0001_initial.py

@@ -1,7 +1,5 @@
 # -*- coding: utf-8 -*-
 # Generated by Django 1.10.5 on 2017-03-15 07:16
-from __future__ import unicode_literals
-
 from django.db import migrations, models
 import django.db.models.deletion
 import modelcluster.fields

bakerydemo/breads/migrations/0002_remove_breadsindexpage_body.py

@@ -1,7 +1,5 @@
 # -*- coding: utf-8 -*-
 # Generated by Django 1.10.5 on 2017-03-26 22:25
-from __future__ import unicode_literals
-
 from django.db import migrations