updated readme

Use `git diff tornado-backend-stage-01:tornado-backend/blog.py react-tornado-api-stage-01:tornado-backend/blog.py` to compare individual files across branches.

### Step 1

### Stage/Step 1

* Starting point is the [Tornado blog demo on GitHub](https://github.com/tornadoweb/tornado/blob/master/demos/blog/blog.py).

* The replication of the Tornado blog demo can be found on branch `tornado-backend-stage-01`.

### Step 2

### Stage/Step 2

* React frontend on top of the Tornado backend.

* This can be found on branch `react-frontend-stage-01`.

  * Addition of the `react-frontend` directory.

  * Addition of the `react-frontend/my-react-app` directory with the react source files created by `create-react-app`.

### Step 3

### Stage/Step 3

* Tornado backend as an API for the react frontend.

* This can be found on branch `react-tornado-api-stage-01`.

  * Addition of `react-frontend/my-react-app/src/components/MessageComponent.js` with an API call to the Tornado backend

  * Update of `tornado-backend/blog.py` with a route and handler to handle requests from `MessageComponent.js`

### Step 4

### Stage/Step 4

* (Full-stack) replication of the Tornado blog demo with react (frontend) and Tornado (backend).

* This can be found on branch `react-tornado-blog-stage-01`.

  * Addition of additinal components in the frontend

  * Addition of additional routes and handlers in the backend

### Step 5

### Stage/Step 5

* Extension of branch `react-tornado-blog-stage-01`

* (Full-stack) replication of the Tornado blog demo with react (frontend), Tornado (backend) and PostgreSQL (backend) served via nginx.

* Extension of branch `react-tornado-blog-stage-02`

* Included nginx service as reverse proxy between front and backend

* Added configuration for serving of static pages via nginx service

* Added persistent pg data bind