Add warning if geocent_time prior isn't specified

Currently, if the prior doesn't contain, it tries to sample and then has a TypeError. We just need a simple check to test if this has been set.

changed milestone to %0.1

assigned to @gregory.ashton

mentioned in commit be79b082

mentioned in merge request !36 (merged)

I see Interferometer has an epoch which is used when adding data. If we add epoch as an option to Interferometer we can just set it when we instantiate and then use a prior on time which is centered at zero and use the epoch to get the absolute time.

mentioned in commit e6d489c6

closed via commit be79b082

closed via merge request !36 (merged)

unassigned @gregory.ashton