Dockerfile out of date

[smpita]

Your upstream docker container boxedcode/alpine-nginx-php-fpm has introduced breaking changes in v1.7.3 resulting in the container closing and the following error:

standard_init_linux.go:190: exec user process caused "exec format error"

I suggest changing FROM boxedcode/alpine-nginx-php-fpm:latest to FROM boxedcode/alpine-nginx-php-fpm:v1.7.2 or otherwise update the dockerfile.