Upgrade pip packages with non-breaking changes

* Django: 2.0.5 -> 2.1
* django-choices -> 1.6.0 -> 1.6.1
* django-countries -> 5.3 -> 5.3.1
* gunicorn: 19.8.1 -> 19.9.0
* Pillow: 5.1.0 -> 5.2.0
* psycopg2-binary: 2.7.4 -> 2.7.5
* pytz: 2018.4 -> 2018.5
* boto3: 1.7.31 -> 1.7.70

Author: ulgens

requirements.txt

@@ -1,21 +1,21 @@
 dj-database-url==0.5.0
 dj-static==0.0.6
-Django==2.0.5
-django-choices==1.6.0
-django-countries==5.3
+Django==2.1
+django-choices==1.6.1
+django-countries==5.3.1
 django-filter==1.1.0
 djangorestframework==3.8.2
-gunicorn==19.8.1
+gunicorn==19.9.0
 Markdown==2.6.11
-Pillow==5.1.0
-psycopg2-binary==2.7.4
+Pillow==5.2.0
+psycopg2-binary==2.7.5
 python-decouple==3.1
-pytz==2018.4
+pytz==2018.5
 static3==0.7.0
-boto3==1.7.31
+boto3==1.7.70
 django-storages==1.6.6
 django-markdownx==2.0.23
 python-slugify==1.2.5
 raven>=3
 django-meta==1.4.1
-django-taggit==0.22.2
+django-taggit==0.22.2