Centered the medium button on the stats screen
Saving today's work

I have begun work making custom stats and maze files load based off of
an index file in a custom maze folder. This will allow for the sharing
of custom maze folders in a future update.
The custom level folder is now self-contained

Custom level directories can now be shared between users with no
changes. Just copy your folder and paste its contents in the new
computer's custom folder.

Next Steps:
Allowing re-ordering of custom levels
Allow choosing an arbitrary custom level directory
Perhaps allow naming custom levels?
(a level name variable already exists, but involving a keyboard may be
cumbersome)