Org-drill updated, now at v2.1

Org-drill updated, now at v2.1

[Paul Sexton]

I Just thought I would let people know I have made extensive updates to 
org-drill recently. Org-drill uses orgmode topics as flashcards for self-testing,
using spaced repetition algorithms like those used in programs such as
SuperMemo, Anki and Mnemosyne. It resides in the contrib directory but has its
own repository at

http://bitbucket.org/eeeickythump/org-drill

Highlights of recent changes:
- new spaced repetition algorithm: a simplified version of SuperMemo SM8,
  in addition to existing SM5 and SM2 algorithms.
- SM5 matrix of optimal factors is now correctly stored as a single
  persistent value, rather than per-item.
- better prioritisation of items within sessions: first failed items, then
  overdue items, then recently learned items, then finally a mix of older +
  new (unlearned) items.
- can now resume drill sessions where you left off, after exiting them via
  edit or quit commands (extremely useful)
- comments and item titles are optionally hidden during review
- almost all customisable variables are declared safe to be file-local

I have used org-drill every day for many months (currently learning Spanish 
using it) and it seems to be pretty robust. If any of you use Anki, etc, 
regularly, please have a look at org-drill -- you may find there is yet 
another job which Emacs can take over for you.

Cheers
Paul