Use WorkingDirectory for the systemd services

Otherwise docker-compose cannot locate environment files referenced
with "env_file".

see:
https://www.freedesktop.org/software/systemd/man/systemd.exec.html
https://docs.docker.com/compose/compose-file/#/envfile

Author: andreaskoch

CHANGELOG.md

@@ -4,6 +4,11 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## [Unreleased]
+
+### Changed
+- Set the working directory (see: https://www.freedesktop.org/software/systemd/man/systemd.exec.html) for the docker-compose systemd services. Otherwise docker-compose cannot locate `env_file`s (see: https://docs.docker.com/compose/compose-file/#/envfile)
+
 ## [v0.1.0-alpha] - 2016-12-18
 
 The prototype

installer.go

@@ -77,8 +77,9 @@ Description={{ .ProjectName }} Service
 After=network.target
 
 [Service]
-ExecStart=/usr/bin/env docker-compose -p "{{ .ProjectName }}" -f "{{ .ProjectDirectory }}/{{ .DockerComposeFile }}" up
-ExecStop=/usr/bin/env docker-compose -p "{{ .ProjectName }}" -f "{{ .ProjectDirectory }}/{{ .DockerComposeFile }}" down
+WorkingDirectory={{ .ProjectDirectory }}
+ExecStart=/usr/bin/env docker-compose -p "{{ .ProjectName }}" -f "{{ .DockerComposeFile }}" up
+ExecStop=/usr/bin/env docker-compose -p "{{ .ProjectName }}" -f "{{ .DockerComposeFile }}" down
 
 [Install]
 WantedBy=network-online.target