Downgrade Docker to Python 3.5 to solve Segmentation Faults (#7799)

Downgrades the Dockerfiles used by Home Assistant to Python 3.5, after
Python 3.6 base image was causing segmentation faults.

See home-assistant/home-assistant#7752

Dockerfile

-FROM python:3.6
+FROM python:3.5
 MAINTAINER Paulus Schoutsen <Paulus@PaulusSchoutsen.nl>
 
 # Uncomment any of the following lines to disable the installation.

virtualization/Docker/Dockerfile.dev

@@ -2,7 +2,7 @@
 # Based on the production Dockerfile, but with development additions.
 # Keep this file as close as possible to the production Dockerfile, so the environments match.
 
-FROM python:3.6
+FROM python:3.5
 MAINTAINER Paulus Schoutsen <Paulus@PaulusSchoutsen.nl>
 
 # Uncomment any of the following lines to disable the installation.