Problems in Dockerfile?

Hi,
I keep playing with your Dockerfile and I wonder whether it would make sense to:

Extend the Path variable as in:
`ENV PATH /opt/conda/envs/beakerx/bin:$PATH`
This would make sure that when running pip it's the one installed in beakerx environment and therefore accessible by the beakerx user. Otherwise the user has to specify this path or define a target when using pip

I have noted that the folder /home/beakerx/.config is only accessible by the root user --- unlike the .config folder in the Jupyter base image. This results in weird problems if I try to pip install packages via git, e.g. if I try to install our (public) company project, e.g.:

`RUN pip install --no-cache-dir git+https://github.com/lobnek/pyutil.git`

This will result in a warning about /home/beakerx/.config but seems to work otherwise.

I find it clumsy to add to my Dockerfile stuff like

```
USER root
RUN chown -R beakerx:beakerx /home/${NB_USER}/.config /home/${NB_USER}/.npm
USER ${NB_USER}
```