I think that I got all details of depth-2 tree impl ironed out, but will
run a side-by-side comparison (the _ccv_icf_rate_weak_classifier with
_ccv_icf_find_best_weak_classifier) to make sure the precomputed results
are used correctly.
remove _ccv_icf_rate_weak_classifier as I am pretty confident on the
implementation now, will work on bootstrapping tmrw. Going to bed now.
Merge remote branch 'liuliu/unstable'