remove some "$" usage in instructions, theres no good way to escape it in nginx literals

bump to 0.2.4

README.md

@@ -35,7 +35,7 @@ docker run --rm --name docker_registry_proxy -it \
        -v $(pwd)/docker_mirror_certs:/ca \
        -e REGISTRIES="k8s.gcr.io gcr.io quay.io your.own.registry another.public.registry" \
        -e AUTH_REGISTRIES="auth.docker.io:dockerhub_username:dockerhub_password your.own.registry:username:password" \
-       rpardini/docker-registry-proxy:0.2.3
+       rpardini/docker-registry-proxy:0.2.4
 ```
 
 Let's say you did this on host `192.168.66.72`, you can then `curl http://192.168.66.72:3128/ca.crt` and get the proxy CA certificate.

nginx.conf

@@ -131,16 +131,6 @@ if [ ! -d /etc/systemd ]; then
    exit 1
 fi
 
-if [[ $EUID -ne 0 ]]; then
-   echo "Must be root to change system files"
-   exit 1
-fi
-
-if [[ $(systemctl is-active --quiet docker.service) -ne 0 ]]; then
-   echo "Docker service missing"
-   exit 1
-fi
-
 mkdir -p /etc/systemd/system/docker.service.d
 cat << EOD > /etc/systemd/system/docker.service.d/http-proxy.conf
 [Service]