In get_nsamples, handle cases where pointing is a non structured dtype, or has no removed field.
Don't impose the Tod/map classes in ProjectionBaseOperator. Implementations should specify it through classin and classout.
Fix nvertices + Docstring.
Version 0.5.
Implement the Layout class.
Implement create_regular_polygon and surface_simple_polygon.
In create_fitsheader, adapt behaviour according to projection type when the cdelt keyword is scalar.
Add test and coverage commands to setup.py.
WCSTo...Operator: set classin and classout to ndarray.
Rename Plane -> DiscreteSurface. Add fromfits method.