Removes kinship values where an animal is less than the minAge

Part of Group Formation

filterAge(kin, ped, minAge = 1)

Arguments

kin	a dataframe with columns id1, id2, and kinship. This is the kinship data reformatted from a matrix, to a long-format table.
ped	dataframe of pedigree information including the IDs listed in "candidates".
minAge	numeric value representing minimum years of age of animals to retain.