Provided certificate expired, will fail local test

[Blaisorblade]

The builtin certificate expired two weeks ago, so it doesn't even work for a testdrive anymore.

EDIT: The following is the server log when a client fails to connect — it explicitly says "sslv3 alert certificate expired".

$ racket -l handin-server
[-|2015-09-08T14:57:37] *** embedded web server started
[-|2015-09-08T14:57:37] Cleaning up all submission directories
[-|2015-09-08T14:57:37] *** handin server started on port 7979
[-|2015-09-08T15:00:10] ERROR: ssl-accept/enable-break: accept failed (error:14094415:SSL routines:SSL3_READ_BYTES:sslv3 alert certificate expired)
^C[-|2015-09-08T15:00:22] user break
[-|2015-09-08T15:00:22] shutting down

Luckily, committing a new certificate is enough to fix this.
Reusing the same common name and duration, and picking reasonably modern parameters, I ran:

openssl req -new -newkey rsa:2048 -sha256 -nodes -x509 -days 3650 -out handin-client/server-cert.pem -keyout handin-server/private-key.pem -subj '/C=US/ST=Utah/L=SLC/O=PLT Scheme Inc./CN=PLT/emailAddress=plt@plscheme-scheme.org'

I'm gonna send a PR doing that, so you can fix it with one click.

(Given the Racket rebranding, maybe you also want to change the common name).