Update firebase-admin to 2.11.0 (#75)

This PR updates [firebase-admin](https://pypi.org/project/firebase-admin) from **2.10.0** to **2.11.0**.



*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/firebase-admin
  - Changelog: https://pyup.io/changelogs/firebase-admin/
  - Homepage: https://firebase.google.com/docs/admin/setup/
</details>

requirements.txt

@@ -1,6 +1,6 @@
 click==6.7
 six==1.11.0
-firebase-admin==2.10.0
+firebase-admin==2.11.0
 
 uvloop==0.10.0
 aiohttp==3.2.1