message: Separate optional arguments from common arguments
  I copy-pasted what is done in RipsComplex. Before that, sphinx was
  grouping nb_points with off_file, as if it couldn't be used with points.
diff: @@ -40,6 +40,8 @@ def choose_n_farthest_points(points=None, off_file='', nb_points=0, starting_poi
  :param off_file: An OFF file style name.
  :type off_file: string
  + And in both cases
  +
  :param nb_points: Number of points of the subsample.
  :type nb_points: unsigned.
  :param starting_point: The iteration starts with the landmark `starting \
  @@ -81,6 +83,8 @@ def pick_n_random_points(points=None, off_file='', nb_points=0):
  :param off_file: An OFF file style name.
  :type off_file: string
  + And in both cases
  +
  :param nb_points: Number of points of the subsample.
  :type nb_points: unsigned.
  :returns: The subsample point set.
  @@ -110,6 +114,8 @@ def sparsify_point_set(points=None, off_file='', min_squared_dist=0.0):
  :param off_file: An OFF file style name.
  :type off_file: string
  + And in both cases
  +
  :param min_squared_dist: Minimum squared distance separating the output \
  points.
  :type min_squared_dist: float.
  