title_case counted small words from the start of the whole string, so
every subtitle that opened with one was set in lower case: 'Aesthetic in
Kant: a Critique', 'Born Fighting: the Scots-Irish'. A colon starts a
title of its own and the first word of one is capitalised however small
it is.
Found by book-pipeline, which had been proposing a title page's capitals
verbatim into a catalogue and needed this to stop.
funkpower