v1.4.0

Added SdfFile.points(drop_invalid=False), which returns the points of the grid as a (num_profiles, num_points, 3) array of x, y and z in metres. With drop_invalid=True it returns the (N, 3) array of the measured points, which point cloud libraries take.

Added a description of the format to the documentation, example scripts for the common use cases, and synthetic sample files of each dialect.