Reintegrate option to output intersections in neighbor deduplication

[julietcohen]

In the neighbor deduplication, the optional functionality to output the intersections is no longer functional since I updated the way we deduplicate with the first package release. This is documented in the function itself here.

If this functionality cannot be reintegrated in the next package release, it would be ideal to output a warning or more descriptive error message if the user sets the return_intersections argument to True. That way, if the user does not really need the intersections to be output, they can at least know to change the argument to False (the default) and move on with their analysis until the intersections output is functional again.

Returning the intersections is helpful for testing the way the neighbor method deduplicates. This feature would be helpful for Ingmar Nitze's lake change dataset, as noted in issue#36.