fix accuracy test and add an euclidean one
fix accuracy test and add an euclidean one

eddelbuettel/annoy,spotify/annoy,eddelbuettel/annoy,eddelbuettel/annoy,spotify/annoy,pombredanne/annoy,spotify/annoy,pombredanne/annoy,eddelbuettel/annoy,pombredanne/annoy,tjrileywisc/annoy,pombredanne/annoy,spotify/annoy,tjrileywisc/annoy,tjrileywisc/annoy,tjrileywisc/annoy