The parsing step is considerably slower in Python, but if parsing
is moved out of the test function, Python wins at 45ms to Rust's 67ms
on 10,000 rounds, presumably due to the overhead of serializing to
Protobuf. Not enough of a difference to justify the inclusion of extra
dependencies and duplicating the lookup code in any case.
We can now show replay buttons for the audio contained in {{FrontSide}}
without having to play it again when the answer is shown.
The template code now always defers FrontSide rendering, as it wasn't
a big saving, and meant the logic had to be implemented twice.
