Changes proposed in this pull request

Allow users to disable support for HTTP/2 by introducing a NO_HTTP2 environment variable for the nginx-proxy container.

This can be achieved by setting NO_HTTP2: "true" in the environment variables.

This is a proposed solution to #1055.

Example

Note: the example only illustrates where the environment variable should be used.

version: '2'
services:
  nginx-proxy:
    image: jwilder/nginx-proxy
    container_name: nginx-proxy
    ports:
      - "80:80"
    volumes:
      - /var/run/docker.sock:/tmp/docker.sock:ro
    environment:
      - NO_HTTP2: "true"

  whoami:
    image: jwilder/whoami
    environment:
      - VIRTUAL_HOST=whoami.local