Make membership registration page faster

[adam-p]

It takes about 5 seconds for the embedded membership registration form to load. This is pushing the limits of how long a visitor will wait before deciding that there's something wrong with the page.

The slowness is (almost certainly) due to the GAE instance warming up. Subsequent loads of the page (when the instance is warm) are fast.

A simple-and-sufficient fix would be to put a wait spinner on the page that gets replaced when the form is loaded. That should keep a user waiting long enough.

A better fix would be to figure out how to keep the GAE instance warm, so there's no start-up time. But it seems that isn't easy, and probably costs money.