Bump default notebook image tag

Use image that includes JupyterHub 0.7.

(c) Copyright IBM Corp. 2016

Author: Justin Tyberg

.env

@@ -15,7 +15,7 @@ DOCKER_MACHINE_NAME=jupyterhub
 DOCKER_NETWORK_NAME=jupyterhub-network
 
 # Single-user Jupyter Notebook server container image
-DOCKER_NOTEBOOK_IMAGE=jupyter/scipy-notebook:2d878db5cbff
+DOCKER_NOTEBOOK_IMAGE=jupyter/scipy-notebook:18e5563b7486
 
 # Notebook directory in the container.
 # This will be /home/jovyan/work if the default