T-001 Show how to make a RecRates out of pairwise marker recombination fractions

[eriqande]

There is currently a place in the vignette where it says that we will describe how to do this. It should be straightforward:

1. Make a marker-pair recombination probability tibble that is derived from the RecRates for the 100 markers that we have
2. Include in the vignette a little thing that shows how to make the changes

Let the format for the recombination rates between markers be the PLINK map format.