Write runIOD function

[moeyensj]

Once we have the IOD functions working, we need an integration function that drives running IOD on clusters and can handle some of the IO corner cases, particularly, how to deal with partial clusters.

This issue is blocked by #6.

[moeyensj]

Critically, this needs to be multiprocessed. Current timing for Gauss is about 20 nanoseconds for a single solution with an added ~3 ms for orbit propagation and ephemeris generation.