Notify channel operation change

[BECATRUE]

This is a half part of #17. Before you start to review, please read the issue carefully.

I implemented only the feature in terms of the channel operation change.

The main features are as follows.

• Use ASGI instead of WSGI (default). For this, I utilized the daphne server, which is the recommended server for Channels.
• Use Channels to implemented WebSockets.

To test this, one can use the codes below.

Client 1: Listen to the operation change

import requests
from websockets.sync.client import connect

HTTP_BASE_URL = 'http://localhost:8000'
WS_BASE_URL = 'ws://localhost:8000'

with requests.Session() as session:
    data = {'username': 'user1', 'password': 'OOOO'}
    response = session.post(HTTP_BASE_URL + '/user/signin/', json=data)
    print(response.status_code)  # 200

    csrf_token = session.cookies.get('csrftoken')
    headers = {'X-CSRFToken': csrf_token}

    with connect(WS_BASE_URL + '/ws/operation/1/', origin='http://localhost:3000') as websocket:
        while True:
            response = websocket.recv()
            print(response)

Client 2: Update the operation status

import time

import requests

HTTP_BASE_URL = 'http://localhost:8000'

with requests.Session() as session:
    data = {'username': 'user2', 'password': 'OOOO'}
    response = session.post(HTTP_BASE_URL + '/user/signin/', json=data)

    csrf_token = session.cookies.get('csrftoken')
    headers = {'X-CSRFToken': csrf_token}

    response = session.post(HTTP_BASE_URL + '/operation/1/', json={'on': True}, headers=headers)
    time.sleep(1)

    response = session.post(HTTP_BASE_URL + '/operation/1/', json={'on': False}, headers=headers)
    time.sleep(1)

    response = session.post(HTTP_BASE_URL + '/operation/1/', json={'on': True}, headers=headers)
    time.sleep(1)

    response = session.post(HTTP_BASE_URL + '/operation/1/', json={'on': False}, headers=headers)
    time.sleep(1)

    response = session.post(HTTP_BASE_URL + '/operation/1/', json={'on': True}, headers=headers)
    time.sleep(1)

    response = session.post(HTTP_BASE_URL + '/operation/1/', json={'on': False}, headers=headers)
    time.sleep(1)

    response = session.post(HTTP_BASE_URL + '/user/signout/', headers=headers)

[BECATRUE]

I will reopen this PR after I complete #34.