outlier_bb_obj: Objective function for outlier model.
In dcgerard/updogAlpha: Using Parental Data for Offspring Genotyping

Objective function for outlier model.

1	outlier_bb_obj(par, ocounts, osize, theta)

`par`	A 2-vector. The first element is the mean of the beta-binomial. The second is the overdispersion parameter.
`ocounts`	A vector of non-negative integers. The ith element is the number of reads of the reference allele in the ith child.
`osize`	A vector of positive integers. The ith element is the total number of reads for the ith child.
`theta`	A vector of proportions. The posterior probabilities of each point being ok.