Outdated docker image on Docker Hub

I encountered an issue with the [h5serv docker image available on Docker Hub](https://hub.docker.com/r/hdfgroup/h5serv).

With this docker image, I was able to access data in h5 files through direct HTTP requests:

`domain = 'my_file_in_root.hdfgroup.org'`
`headers = {'host': domain}`
`endpoint = 'http://127.0.0.1:5000'`

`# get root uuid`
`req = endpoint + '/'`
`rsp = requests.get(req, headers=headers)`
`domain_json = rsp.json()`
`root_uuid = domain_json['root']`

However, I was not able to access the data using h5pyd. In fact, I was encountering the same problem as described in [issue 60](https://github.com/HDFGroup/h5pyd/issues/60).

Interestingly, the following command

`f = h5pyd.File('my_file_in_root.hdfgroup.org', 'r', endpoint='http://127.0.0.1:5000')`
`f_uuid = f.id.uuid`

would return a different f_uuid than root_uuid from a direct HTTP request as above.

Eventually, I realized that the image on Docker Hub is 2 years old, and thus probably outdated. I proceeded with manual installation of h5serv as described [here](https://h5serv.readthedocs.io/en/latest/Installation/ServerSetup.html#installing-on-linux-mac-os-x). And then created a new docker image manually using the local installation of h5serv. With this new docker image, everything seems to work properly.