Add Haversine lat/long and jaccard set-distance comparators to the library

Define two new comparators:
- A Haversine lat/long distance, returning distance in km given decimal lat/long values
- A Jaccard set distance, returning the decimal Jaccard similarity

Note that both assume they will get a single field for each record. E.g., the haversine distance assumes it will get a string of form <lat><delim><long>. This is kind of inefficient, but it wasn't clear that there was a good way to do multi-field comparisons. 

Per timeit, timing on the haversine distance averages 4.8us. Timing on the jaccard distance averages 2.72 us.