Run command as host's user

Add a script in charge of creating dummy user with host's user's uid and guid. Then run the command
As this script in the entrypoint of the docker file it should keep BC.

here is my composer alias who works without makefile
alias composer=docker run -ti --rm -e DOCKER_UID=`id -u` -e DOCKER_GID=`id -g` -e DOCKER_SSH=/tmp/ssh -v ~/.ssh:/tmp/ssh -v `pwd`:/srv -w /srv marmelab/composer-hhvm hhvm /usr/local/bin/composer