Update icon.
Change lookup URL.

The new URL is
http://steinbrenner.mysdhc.org/teacher/0089colangelo/fliptheclassroom.txt,
which is a file hosted on a domain the filter can't block. (GitHub
itself was already filtered by the firewall, and it's only a matter of
time before GH Pages is also blocked.) The new file is hosted on the
school domain where Mr. Colangelo can change it relatively easily.