Little issue of versioning due to jupyterlab

**Following the ReadMe instructions**

An error occurs when we intend to install the bokeh extension to display bokeh pictures within jupyter
```
jupyter labextension install jupyterlab_bokeh
```
We retrieve the following error due to conflicting versions of JupyterLab obviously.
```
ValueError: No version of jupyterlab_bokeh could be found that is compatible with the current version of JupyterLab.

Conflicting Dependencies:
JupyterLab Extension Package
>=1.2.1 <1.3.0 >=0.19.1 <0.20.0@jupyterlab/application
>=1.2.1 <1.3.0 >=0.19.1 <0.20.0@jupyterlab/apputils
>=1.2.2 <1.3.0 >=0.19.1 <0.20.0@jupyterlab/notebook
>=4.2.0 <4.3.0 >=3.2.1 <4.0.0 @jupyterlab/services
See the log file for details: /var/folders/ps/bh4l2sdn40v1shp45y8pkl4h0000gn/T/jupyterlab-debug-i7_7dpdj.log

```

I tried to update jupyterlab, but the error remains.