breed: Breed valid individuals
In pwhigham/spatibm: A Spatial Individual-based model for land-based organisms

For each closest pair of male/females, create fecund number of children, and place them around the midpoint of the location between the parents, displaced from this point by displace as an isotropic placement. Once parents are seperated by > max.dist breeding stops.

1	breed(pts, b.pairs, b.table)

`pts`	The points representing individuals that are available for breeding
`b.pairs`	The breeding pairs as a matrix returned from `breeding.pairs`. Each row is <female> <male> index into `pts`.
`b.table`	Breeding table. This is used to extract the number of children to produce and displacement of children drawn from normal distribution around the mid-point in space between the male and female parents.