update some file names

default config file is now `jupyterhub_config.py`,
to be consistent with everything else

add config files, runtime files to .gitignore

examples/sudo/jupyterhub_config.py

@@ -0,0 +1,7 @@
+# Configuration file for jupyterhub
+
+c = get_config()
+
+c.JupyterHubApp.admin_users = {'rhea'}
+c.LocalProcessSpawner.set_user = 'sudo'
+c.Authenticator.whitelist = {'ganymede', 'io', 'rhea'}