Update docker build instructions and docker compose to use latest version of Alpine, PostgreSQL and postgres-websockets [fix #49]

Author: diogob

Dockerfile

@@ -1,5 +1,5 @@
 # Use Alpine Linux as base image
-FROM alpine:3.8
+FROM alpine:3.11.6
 
 # Install libpq and gmp dependencies (dynamic libraries required by the project)
 RUN apk update && apk add libpq gmp libffi
@@ -18,6 +18,6 @@ ENV PGWS_DB_URI= \
 
 # Run the binary on container start
 # (substitute your project name for 'example')
-CMD ["postgres-websockets", "/etc/postgres-websockets.conf"]
+CMD postgres-websockets
 
 EXPOSE 3000

Dockerfile.build

@@ -1,4 +1,4 @@
-FROM alpine:3.8
+FROM alpine:3.11.6
 
 RUN echo "@testing http://nl.alpinelinux.org/alpine/edge/testing" >> /etc/apk/repositories
 RUN apk -U add shadow@testing

docker-compose.yml

@@ -1,7 +1,7 @@
 version: '3'
 services:
   db:
-    image: postgres:10-alpine
+    image: postgres:12-alpine
     ports:
         - "5433:5432"
     environment:
@@ -12,6 +12,7 @@ services:
     environment:
       PGWS_DB_URI: postgres://pgws:example@db/pgws
       PGWS_JWT_SECRET: "auwhfdnskjhewfi34uwehdlaehsfkuaeiskjnfduierhfsiweskjcnzeiluwhskdewishdnpwe"
+      PGWS_ROOT_PATH: /home/postgres-websockets/client-example
     ports:
         - "3000:3000"
     depends_on: