In the ongoing struggle with Circle CI-specific test failures, the
preparatory `meteor --get-ready` has been a consistent point of failure,
before any real tests have the chance to run.
Using a lighter-weight command (meteor --help) that still does most of
what --get-ready did seems worth a try, though it might just defer
memory-intensive work until later, so we'll have to see what happens.
We (@abernix and I) suspect the intermittent "died unexpectedly" failures
of `meteor --get-ready` on Circle CI are due to hitting their (low) limit
on the maximum number of open files.
Although optimistic caching speeds up rebuilds considerably, it doesn't do
much for initial builds, and it definitely keeps more files open.
Disabling it here seems worth a try.
