bootstrap.sh can't support Unix.

I think docker/bootstrap.sh is written in Windows.
I build it then run it:
```
docker build -t zkui:2.0 .
docker-compose up -d zkui
```
then run it, it report errors. `/bin/sh^M: bad interpreter: No such file or directory`
this is my docker-compose.yaml
```
version: "3"
services:
zookeeper:
image: zookeeper:3.4.13
restart: always
ports:
- "2181:2181"
zkui:
image: zkui:2.0
ports:
- "9090:9090"
environment:
- ZK_SERVER=zookeeper:2181
volumes:
- /var/run/docker.sock:/var/run/docker.sock
depends_on:
- zookeeper
```
I have solve this problem, I rewrote bootstrap.sh in Linux.