Merge #130

130: Scheduled weekly dependency update for week 15 r=mithrandi a=pyup-bot






### Update [ipaddress](https://pypi.org/project/ipaddress) from **1.0.19** to **1.0.21**.


*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/ipaddress
  - Repo: https://github.com/phihag/ipaddress
</details>

requirements.txt

@@ -13,7 +13,7 @@ cryptography==2.2.2
 enum34==1.1.6
 idna==2.6
 incremental==17.5.0
-ipaddress==1.0.19
+ipaddress==1.0.21
 lxml==4.2.1
 packaging==17.1
 pyasn1-modules==0.2.1