For now compose_helpers only includes FakeComposeBox.
I don't love either of the names, but some of the alternatives
that I thought of have their own tradeoffs.
The compose_helpers module will soon have other
helper classes or functions in it, possibly including
the mock_banners helper from lib/compose_banner.
I don't want to step on mock_banners yet, because
I have two possible plans for improving that code,
and I haven't decided what's best yet, so for now
I don't want to step on it or move it, so I am
just leaving that alone for now.
Gotta start somewhere.
