build fixes and readme improvements (#85)

* add compose to the build image
* update readme
* fine tuning for build container
* directly pass commands to run script in build env
* fix dockerfile so that everything can be build on Docker version 17.05.0-ce, build 9f07f0e-synology

build/run.sh

@@ -1,8 +1,10 @@
 #!/bin/sh
+if [ ! $(id -u) -eq 0 ]; then
+	echo "This script may need to be run as root to be able to use docker/docker-compose through it."
+fi
 docker run \
 	--rm -it \
 	-u $(id -u ${USER}):$(id -g ${USER}) \
 	-v /var/run/docker.sock:/var/run/docker.sock \
 	-v ${PWD}/..:/kopano-docker/ \
-	$(docker build -q .)
-
+	$(docker build -q .) $@