This script will request and install a certificate, then recycle your web
server.  This is barely sufficient, but a lot more needs to be done...
1) Tracking certificate expiration, and only placing a new order when
   appropriate.
2) Handling failure better.
3) Handle changes in the system password (like anyone ever does THAT).
4) Clean up stale authorizations.

Also, some enhanced features would be nice:
1) Adding a bunch of SANs, so virtual hosts Just Work
2) Key aging and updating
3) More control of certificate contents... I can't find a list of what
   Let's Encrypt supports in CSRs.