Sub to only personals by default

Rather than subbing to classes by default, sub only to personals. This removes
the need for the dev.py script, since main.py can be used directly. It also
eases running multiple production Chiron instances -- for example, one as
daemon/chiron and one as daemon/chiron.mit.edu.
Expand description of running Chiron

Talk more about the primary production deployment vs. private deployments,
reflect main.py's new option, and expunge mention of dev.py in preparation for
killing it.
Kill dev.py

The last two commits have made it unnecessary and removed it from the docs, so
go ahead and delete it.
Treat all zephyrs as UTF-8

Apparently basically all zephyrs are UTF-8, but the charset field usually lies.
Given that, if we want to handle Unicode in zephyrs, we probably just want to
assume everybody sends UTF-8 (especially since python-zephyr doesn't seem to
expose the charset field...).
Add Unicode character lookup (Chiron-#22)
Support "Linerva" tickets (Chiron-#15)
Add etherpad.mit.edu's Trac (Chiron-#29)

We don't use the "etherpad" name because the SIPB etherpad Trac is so tiny it
seems reasonably likely we'll want "Etherpad #1234" to mean "upstream Etherpad
ticket #1234" at some point.
Ignore matches that are strictly contained in other matches (chiron-#11)

Signed-off-by: Anders Kaseorg <andersk@mit.edu>
Remove superfluous is_personal definition

Back in 7019556, I added an is_personal function so that MIT class numbers in
personals would produce a response. By the time 726fef6a came around and I
wanted to disable the timeout for personals, I'd apparently forgotten, so I
added an identically-named equivalent function. This punts the newer one.
Default tracker in instance for personals

On test classes, we accept a default tracker in the instance. When looking up a
bunch of tickets from one project, this behavior is quite useful, so broaden it
to personals as well. Fixes Chiron-#24.