Update to Apache Toree 0.3.0-incubating RC1

The RC1 contains the fix to support latest release of JupyterLab.

Fixes #710

all-spark-notebook/Dockerfile

@@ -34,7 +34,7 @@ RUN conda install --quiet --yes \
 
 # Apache Toree kernel
 RUN pip install --no-cache-dir \
-    https://dist.apache.org/repos/dist/dev/incubator/toree/0.2.0-incubating-rc5/toree-pip/toree-0.2.0.tar.gz \
+    https://dist.apache.org/repos/dist/dev/incubator/toree/0.3.0-incubating-rc1/toree-pip/toree-0.3.0.tar.gz \
     && \
     jupyter toree install --sys-prefix && \
     rm -rf /home/$NB_USER/.local && \