fix json-server (FIX #187)

json-server/Dockerfile

@@ -2,16 +2,16 @@
 # Dockerfile for json-server
 #
 
-FROM alpine
-MAINTAINER kev <noreply@easypi.pro>
-
-WORKDIR /data
+FROM alpine:3
+MAINTAINER EasyPi Software Foundation
 
 RUN set -xe \
     && apk add --no-cache nodejs nodejs-npm \
     && npm install -g json-server \
     && rm -rf /tmp/npm* /var/cache/apk/*
 
+WORKDIR /data
+
 EXPOSE 3000
 
 ENTRYPOINT ["json-server"]