Update django to 2.1.2 (#360)

This PR updates [Django](https://pypi.org/project/Django) from **2.1.1** to **2.1.2**.



<details>
  <summary>Changelog</summary>
  
  
   ### 2.1.2
   ```
   ==========================

*October 1, 2018*

Django 2.1.2 fixes a security issue and several bugs in 2.1.1. Also, the latest
string translations from Transifex are incorporated.

CVE-2018-16984: Password hash disclosure to &quot;view only&quot; admin users
===================================================================

If an admin user has the change permission to the user model, only part of the
password hash is displayed in the change form. Admin users with the view (but
not change) permission to the user model were displayed the entire hash. While
it&#39;s typically infeasible to reverse a strong password hash, if your site uses
weaker password hashing algorithms such as MD5 or SHA1, it could be a problem.

Bugfixes
========

* Fixed a regression where nonexistent joins in ``F()`` no longer raised
  ``FieldError`` (:ticket:`29727`).

* Fixed a regression where files starting with a tilde or underscore weren&#39;t
  ignored by the migrations loader (:ticket:`29749`).

* Made migrations detect changes to ``Meta.default_related_name``
  (:ticket:`29755`).

* Added compatibility for ``cx_Oracle`` 7 (:ticket:`29759`).

* Fixed a regression in Django 2.0 where unique index names weren&#39;t quoted
  (:ticket:`29778`).

* Fixed a regression where sliced queries with multiple columns with the same
  name crashed on Oracle 12.1 (:ticket:`29630`).

* Fixed a crash when a user with the view (but not change) permission made a
  POST request to an admin user change form (:ticket:`29809`).


==========================
   ```
   
  
</details>


 

<details>
  <summary>Links</summary>
  
  - PyPI: https://pypi.org/project/django
  - Changelog: https://pyup.io/changelogs/django/
  - Homepage: https://www.djangoproject.com/
</details>

requirements.txt

@@ -1,8 +1,8 @@
 -c constraints.txt
 
-Django==2.1.1 \
-    --hash=sha256:04f2e423f2e60943c02bd2959174b844f7d1bcd19eabb7f8e4282999958021fd \
-    --hash=sha256:e1cc1cd6b658aa4e052f5f2b148bfda08091d7c3558529708342e37e4e33f72c
+Django==2.1.2 \
+    --hash=sha256:acdcc1f61fdb0a0c82a1d3bf1879a414e7732ea894a7632af7f6d66ec7ab5bb3 \
+    --hash=sha256:efbcad7ebb47daafbcead109b38a5bd519a3c3cd92c6ed0f691ff97fcdd16b45
 Jinja2==2.10 \
     --hash=sha256:74c935a1b8bb9a3947c50a54766a969d4846290e1e788ea44c1392163723c3bd \
     --hash=sha256:f84be1bb0040caca4cea721fcbbbbd61f9be9464ca236387158b0feea01914a4