Add introduction and collaboration text to README

Signed-off-by: Alex Nelson <a.nelson@prometheuscomputing.com>
Add text describing input data

Sign-offs in alphabetical order.

Signed-off-by: Mary Laamanen <mary.laamanen@nist.gov>
Signed-off-by: Alex Nelson <a.nelson@prometheuscomputing.com>
Signed-off-by: Doug White <douglas.white@nist.gov>