Add optional timeout feature

[nickjer]

Allow the user to choose the ability to have the Jupyter server timeout after 10 minutes of inactivity. This can be achieved with the configuration options:

NotebookApp.shutdown_no_activity_timeout

and

MappingKernelManager.cull_idle_timeout

See http://jupyter-notebook.readthedocs.io/en/stable/config.html for more information.