Summary of changes in JupyterHub

See git log for a more detailed summary.

0.5

Single-user server must be run with Jupyter Notebook ≥ 4.0
Require --no-ssl confirmation to allow the Hub to be run without SSL (e.g. behind SSL termination in nginx)
Add lengths to text fields for MySQL support
Add Spawner.disable_user_config for preventing user-owned configuration from modifying single-user servers.
Fixes for MySQL support.
Add ability to run each user's server on its own subdomain. Requires wildcard DNS and wildcard SSL to be feasible. Enable subdomains by setting JupyterHub.subdomain_host = 'https://jupyterhub.domain.tld[:port]'.
Use 127.0.0.1 for local communication instead of localhost, avoiding issues with DNS on some systems.
Fix race that could add users to proxy prematurely if spawning is slow.

Fix removal of /login page in 0.4.0, breaking some OAuth providers.

Add Spawner.user_options_form for specifying an HTML form to present to users, allowing users to influence the spawning of their own servers.
Add Authenticator.pre_spawn_start and Authenticator.post_spawn_stop hooks, so that Authenticators can do setup or teardown (e.g. passing credentials to Spawner, mounting data sources, etc.). These methods are typically used with custom Authenticator+Spawner pairs.
0.4 will be the last JupyterHub release where single-user servers running IPython 3 is supported instead of Notebook ≥ 4.0.

No longer make the user starting the Hub an admin
start PAM sessions on login
hooks for Authenticators to fire before spawners start and after they stop, allowing deeper interaction between Spawner/Authenticator pairs.
login redirect fixes

First preview release