Instead of being a scroll window inside a scroll window, the show
description now shows just the first paragraph by default, then displays
a "Read More" button if there is more to the description. Clicking the
button reveals the rest.
Currently, to keep the button from glitching when updating it from the
size-allocate signal, a GtkRevealer with a transition-duration of
1 millisecond is used. It's a hacky workaround but I'm not quite sure
how to do it better.
Fixes#81
