Finalized Jupyterlab for the sprint

Dockerfile

-FROM jupyter/scipy-notebook:hub-1.5.0
+FROM jupyter/datascience-notebook:hub-3.1.1
 
 # Install from APT repository
 USER root
@@ -9,8 +9,8 @@ RUN apt-get install -y git
 USER jovyan
 RUN pip3 install --upgrade pip
 
-# Install 'nice to have lab extensions'
-# RUN pip install --upgrade jupyterlab
-RUN pip install jupyterlab-git==0.34.0
+RUN pip3 install --upgrade pip
+RUN pip install jupyter-server-proxy==4.0.0
+RUN pip install jupyterlab-git==0.42.0
 RUN pip install jupyterlab-gitlab==3.0.0