accept implicit port 80 on whitelist

[bryevdv]

Reference: request/request#515

Many programs strip the port from the host header when it is 80, and this breaks our whitelist checking. This prevents the server from being run behind a proxy on port 80.

[havocp]

lgtm. it might not hurt to test a couple actual http requests (I added stuff to test_server.py which should make that simple now). In case tornado ever does something unexpected before we see the Host value or something.

[havocp]

lgtm. could add a websocket test for this case

[bryevdv]

I tested this on a locally running nginx with this configuration:

worker_processes auto;

error_log   /tmp/error.log;
pid         /tmp/nginx.pid;

events {
    worker_connections  1024;
}

http {
    default_type    application/octet-stream;

    sendfile            on;
    tcp_nopush          on;
    tcp_nodelay         on;

    keepalive_timeout   65;
    types_hash_max_size 2048;

    server {
        listen 80 default_server;
        server_name _;

        access_log  /tmp/bokeh.access.log;
        error_log   /tmp/bokeh.error.log  debug;

        location /apps/ {
            proxy_pass http://127.0.0.1:5100;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection "upgrade";
            proxy_http_version 1.1;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header Host $host:$server_port;
            proxy_buffering off;
        }

        location /static {
            alias /Users/bryan/work/bokeh/bokeh/server/static;
        }
    }
}

And running the server with:

bokeh serve sliders.py  --prefix=apps/ --address=127.0.0.1 --port 5100 --host localhost:80

[bryevdv]

I'm using the same whitelist checker in both cases, and the checker has tests, is that sufficient?