internal function for generating cardinal ranks
cardinalize(x)input vector
returns new vector of cardinal rank scores
converts raw Elo scores into predicted number of individuals beaten (using Equation 1 from paper)
subtracting .5 is equivalent to removing the prob of winning against oneself because 1/(1 + exp(-0.01*0)) = 1/(1 + exp(0)) = 1/(1 + 1) = 1/2