Rephase: update the document for docker

- *The manual schema initial script is in `https://github.com/apache/incubator-shardingsphere-example/blob/dev/src/resources/manual_schema.sql`, please execute it before you first run the example.*

- *Please make sure master-slave data sync on MySQL is running correctly. Otherwise this example will query empty data from slave.*

## Before start the example

please make sure some dependencies from [shardingsphere](https://github.com/apache/incubator-shardingsphere) and [shardingsphere-spi-impl](https://github.com/OpenSharding/shardingsphere-spi-impl) have been installed since some examples depend on that.

if you are a newbie for shardingsphere, you could prepare the dependencies as following : 

1.download and install [shardingsphere](https://github.com/apache/incubator-shardingsphere) :  

```bash

## download the code of shardingsphere

git clone https://github.com/apache/incubator-shardingsphere.git

## checkout a specific version, say 4.0.0-RC1

cd incubator-shardingsphere && git checkout 4.0.0-RC1

## install the dependencies

mvn clean install -Prelease

```

2.download and install [shardingsphere-spi-impl](https://github.com/OpenSharding/shardingsphere-spi-impl) :  

```bash

## download the code of shardingsphere-spi-impl

git clone https://github.com/OpenSharding/shardingsphere-spi-impl.git

## checkout a specific version, say 4.0.0-RC1

cd shardingsphere-spi-impl && git checkout 4.0.0-RC1

## install the dependencies

mvn clean install

```

## sharding-sphere-example module design

### project module

## Using docker-compose to config startup environment

before we use docker compose, please install docker first : https://docs.docker.com/compose/install/

before we use docker compose, please install docker and docker-compose first : https://docs.docker.com/compose/install/

#### sharding-jdbc

1. access the docker folder (cd docker/sharding-jdbc/sharding)

2. launch the environment by docker compose (docker-compose up -d)

3. access mysql / etcd / zookeeper as you want

4. if there is conflict on port, just modify the mapper port in docker-compose.yml and then launch docker compose again(docker-compose up -d)

4. if there is conflict on port, just modify the corresponding port defined in docker-compose.yml and then launch docker compose again(docker-compose up -d)

5. if you want to stop these environment, use command docker-compose down

#### sharding-proxy

1. access the docker folder (cd docker/sharding-proxy/sharding)

2. launch the environment by docker compose (docker-compose up -d)

3. access proxy by `mysql -h127.0.0.1 -P13308 -proot -uroot`

4. if there is conflict on port, just modify the mapper port in docker-compose.yml and then launch docker compose again(docker-compose up -d)

4. if there is conflict on port, just modify the corresponding port defined in docker-compose.yml and then launch docker compose again(docker-compose up -d)

5. if you want to stop these environment, use command docker-compose down

to clean the docker container , you could use docker rm `docker ps -a -q` (be careful)