ENH: added trial definition starting from the end
ENH: remove extra check code (reuse it if you don't trust the results
DOC: help of event2trl_decay
DOC: rename powcorr to infocol to make its meaning more general
ENH: added decay_into_r, which does not average over trials
DOC: explain why there is a 0
ENH: LMM on decay of alpha