Mailing list retirement

[Jason Evans]

This mailing list is now retired, as part of consolidating all project management on GitHub.  To track future releases, use one of the mechanisms documented in the "Project activity" section of the primary website, which is now at:

	http://jemalloc.net/

Note that the mailing list archives will remain available, currently at:

	http://jemalloc.net/mailman/jemalloc-announce/index.html