Run as bashttpd user

Fixes the warning from bashttpd that it should not be run as root

Dockerfile

@@ -1,4 +1,8 @@
 FROM alpine:3.6
+RUN addgroup -g 1000 -S bashttpd && \
+    adduser -u 1000 -S bashttpd -G bashttpd
+WORKDIR /home/bashttpd
 RUN apk add --no-cache bash socat
 COPY . .
-CMD ["socat", "TCP4-LISTEN:8080,fork", "EXEC:/bashttpd"]
+USER bashttpd
+CMD ["socat", "TCP4-LISTEN:8080,fork", "EXEC:./bashttpd"]