Add offset to windows so that they can be computed centered if desired.
Change add_features to deduplicate points on the way in. Kristina's data
had some duplicate points that were messing up tests. Deduplication is
performed based on MMSI, segment ID and time.
With deduplicated points and zero offset, the new add measures code produces
identical output to the original code.
closes #69
add_featuresto deduplicate points on the way in. Kristina's data had some duplicate points that were messing up tests. Deduplication is performed based on MMSI, segment ID and time.With deduplicated points and zero offset, the new add measures code produces identical output to the original code.