fix ordering after interpolation
There's a bug when using both time and distance marginalisation with a reduced time window for the prior as noticed in !296 (merged).
The interpolation in the distance lookup was sorting the output likelihoods. This MR fixes that by rearranging the output likelihoods to have the original indices. See https://stackoverflow.com/questions/44941271/scipy-interp2d-returned-function-sorts-input-argument-automatically-and-undesira for where the solution came from.