Release v4.0.0

Merge pull request #127 from krassowski/3.0.1

Release 3.0.1 to pick up updated readme file

Merge pull request #98 from ian-r-rose/jupyterlab-2.0

Jupyterlab 2.0

Publish v1.0.0-pre.1

Release v0.10.0.

Merge pull request #67 from ian-r-rose/0.34

Updates for JupyterLab 0.34

Merge pull request #60 from ian-r-rose/jlab0.33

Updates for 0.33