optimize building process by merging layers

Dockerfile

@@ -7,19 +7,10 @@ ADD environment.yml /tmp/environment.yml
 USER root
 RUN sed -i "s|name\: jupyter-example-profile|name\: base|g" /tmp/environment.yml # we need to replace the name of the environment with base such that we can update the base environment here
 USER $NB_USER
-RUN conda env update -f /tmp/environment.yml # All packages specified in environment.yml are installed in the base environment
 
-# Execute postBuild script
-ADD postBuild.sh /tmp/postBuild.sh
-# Make the file executable (TODO: is this still needed?)
-USER root 
-RUN chmod +x /tmp/postBuild.sh
-# 
-USER $NB_USER
-RUN /tmp/postBuild.sh
-
-# Cleanup conda packages
-RUN conda clean --all -f -y
+# All packages specified in environment.yml are installed in the base environment
+RUN conda env update -f /tmp/environment.yml && \
+    conda clean -a -f -y
 
 ENV JUPYTER_ENABLE_LAB=yes