TODO items for public-inbox

(Not in any particular order)

* implement RFC 4685 (Atom message threading)
* configurable constants (quote folding, index limits)
* use tags as date-based skiplists for navigating history
  (maybe not needed with Xapian support nowadays?)
* handle Xapian date range queries:
  http://mid.gmane.org/20151005222157.GE5880@survex.com
* use REQUEST_URI properly for CGI / mod_perl2 compatibility
  with Message-IDs which include '%'
* more test cases (use git fast-import to speed up creation)
* large mbox/Maildir/MH/NNTP spool import (use git fast-import)
* remove dependency on ssoma installation (inline the code)
* improve + document mlmmj integration, currently only at:
  http://bogomips.org/unicorn-public/20140508084301.GA2033%40dcvr.yhbt.net/