Genotypes as a compressed R data object (*.rds)

Genotypes matrix (markers x samples) as an R data object for use with the `argyle` package (https://github.com/andrewparkermorgan/argyle). The object itself is just a matrix, with marker and sample metadata as attributes. For details see the `argyle` manuscript: Morgan AP (2016) argyle: an R package for analysis of Illumina genotyping arrays. G3 6: 281-286. http://www.g3journal.org/content/6/2/281