naughty: Don't interpret markup in titles

Since only the body text of a notification may contain markup,
by combining the two together and calling set_markup(), the
title would also get interpreted as if it had markup.
This could be seen with:
$ notify-send "Title & text" "<i>body text</i>"

The unescaped & would get interpreted as broken markup and so
naughty would fall back to escaping everything which would make
the "<i>" tags be shown rather than interpreted.

So, the title must always be escaped so that it is not interpreted
as markup.

Signed-off-by: Ross Lagerwall <rosslagerwall@gmail.com>
Signed-off-by: Uli Schlachter <psychon@znc.in>