Add support for Debian Bullseye

Added `on_delete` attributes, updated ForceCanonicalHostnameMiddleware for
compatibility and added Dockerfile for Bullseye.

Add Debian Buster dockerfile

Runs fine on Buster!

Red Hat last donated to SFC on 2020-03-27.

The logo should have been removed sooner, but they kept saying they
were going to donate again and never did.

A bit more width for the video, remove <p>

Ok, that was too small, try this.

Put Karen's doctorate as our featured item.

The video may not work there, but going to try it.

smile.amazon.com deprecated

add random file

Clarify filing year / fiscal year numbers

All of this is very confusing, because the IRS requires you use the
Form 990 for the year in which your fiscal year starts, but most
accountants tend to call the fiscal year by the year number of when
the fiscal year *ends*. Plus, ours ends so early in the next
calendar year, that it's extremely confusing.

Normalize at least the text on the transparency page to use a
hyphenated FY designation, and also add what IRS considers the filing
year to be.

add new tshirt design to /sustainers

fixed width on 'Become a Sustainer' button

use utf-8 encoding to get local testing working

also patched urls.py for easier changing of static locations for
local testing