add binary search sampling
add binary search sampling

tgvaughan/beast2,tgvaughan/beast2,tgvaughan/beast2,CompEvol/beast2,CompEvol/beast2,tgvaughan/beast2,Anaphory/beast2,Anaphory/beast2,Anaphory/beast2,CompEvol/beast2,Anaphory/beast2,CompEvol/beast2