Update pytz to 2018.7 (#402)

This PR updates [pytz](https://pypi.org/project/pytz) from **2018.6** to **2018.7**.



*The bot wasn't able to find a changelog for this release. [Got an idea?](https://github.com/pyupio/changelogs/issues/new)*

<details>
  <summary>Links</summary>
  
  - PyPI: https://pypi.org/project/pytz
  - Homepage: http://pythonhosted.org/pytz
  - Docs: https://pythonhosted.org/pytz/
</details>

Author: pyup-bot

requirements.txt

@@ -181,9 +181,9 @@ pygments-lexer-babylon==0.12.0 \
 optisorl==0.2.1 \
     --hash=sha256:808f22b6d4da608a255f40792e80cf8483f443425dbcb5f18ebe236295c19bbf \
     --hash=sha256:4b18d8a270075aa0fe9588790162c03a80e822237e3346a2817d6e82236f1a49
-pytz==2018.6 \
-    --hash=sha256:91e3ccf2c344ffaa6defba1ce7f38f97026943f675b7703f44789768e4cb0ece \
-    --hash=sha256:642253af8eae734d1509fc6ac9c1aee5e5b69d76392660889979b9870610a46b
+pytz==2018.7 \
+    --hash=sha256:8e0f8568c118d3077b46be7d654cc8167fa916092e28320cde048e54bfc9f1e6 \
+    --hash=sha256:31cb35c89bd7d333cd32c5f278fca91b523b0834369e757f4c5641ea252236ca
 django-jinja==2.4.1 \
     --hash=sha256:ceaa0eeebc4d91a5800967e50f4f087f0b6457503e3c2af85dc199bed8732a9a \
     --hash=sha256:8a49d73de616a12075eee14c6d3bbab936261a463457d40348d8b8e2995cfbed