install: store redmine applications logs @ /var/log/redmine/redmine/
install: store redmine vhost logs @ /var/log/redmine/nginx/
install: store supervisor logs @ /var/log/redmine/supervisor/
install: setup a logrotation job for redmine-vhost logs
install: indentation fixes
dockerfile: added volume mount instruction for `/var/log/redmine`
changelog: updated
Merge branch 'logs-volume'

Closes #52