Use supervisor and fixup env generation

supervisor/puma.conf

@@ -0,0 +1,13 @@
+[program:puma]
+priority=10
+directory=/app/code
+environment=HOME=/app/code,RAILS_ENV=production,PORT=3000
+command=bundle exec puma -C config/puma.rb
+user=cloudron
+autostart=true
+autorestart=true
+stopsignal=QUIT
+stdout_logfile=/dev/stdout
+stdout_logfile_maxbytes=0
+stderr_logfile=/dev/stderr
+stderr_logfile_maxbytes=0