Add in a note about performance. Not sure I got the cross-reference stuff right though.
Add in a note about performance. Not sure I got the cross-reference stuff right
though.

--HG--
extra : convert_revision : svn%3A14d46d22-621c-0410-bb3d-6f67920f7d95/trunk%401877

infowantstobeseen/pyglet-darwincore,infowantstobeseen/pyglet-darwincore,infowantstobeseen/pyglet-darwincore,infowantstobeseen/pyglet-darwincore,infowantstobeseen/pyglet-darwincore