Docker higlass-container fails to start if userns-remap is in use

Hi,

We have `"userns-remap": "docker"` set in our `/etc/docker/daemon.json` to prevent Docker apps from running as root. Doing this causes the higlass-container Docker container to fail to start:

```
[root@higlass ~]# docker run --detach \
> --publish 8989:80 \
> --volume ~/hg-data:/data/higlass/hg-data \
> --volume ~/hg-tmp:/data/higlass/hg-tmp \
> --name higlass-container \
> higlass/higlass-docker:v0.6.1
fc5b14d74f514f02598cfce87e06a86895e13e922feb384d8761c45f0fcc1273
/usr/bin/docker-current: Error response from daemon: oci runtime error: container_linux.go:235: starting container process caused "container init exited prematurely".
```

It's not clear what the image/container is trying to do, but it's a bit concerning that this appears to need to be run as root at the moment.