rm nginx configs on debian purge

debian/postrm

@@ -24,6 +24,8 @@ main() {
   (nginx -t && service nginx reload) || true
 
   if [[ "$1" == "purge" ]]; then
+    rm -f /etc/nginx/conf.d/dokku.conf
+    rm -f /etc/nginx/conf.d/dokku-installer.conf
     rm -f ${DOKKU_ROOT}/.dokkurc ${DOKKU_ROOT}/dokkurc ${DOKKU_ROOT}/tls
     rm -f ${DOKKU_ROOT}/.ssh/authorized_keys ${DOKKU_ROOT}/.sshcommand
     rm -f ${DOKKU_ROOT}/ENV ${DOKKU_ROOT}/HOSTNAME ${DOKKU_ROOT}/VERSION