Archive old user number estimates and graphing code
The user number graphs produced by legacy/trac#8462 (moved) will soon replace the existing user number graphs. See also the announcement on tor-dev@: https://lists.torproject.org/pipermail/tor-dev/2013-September/005443.html
We should archive the old user number estimates and graphing code and make it easy for people to generate the old graphs if they want.