Fix failure in Projection.write
Small improvements to docs
Preserved requested spectral unit
Tidy up initialization of new cubes from modified version of existing cubes.
Set _spectral_unit only in with_spectral_unit
Minor fix
Pass new meta
Fix propagation of spectral unit
Check that WCS auto-changes unit and that spectral_unit is needed
Fix error in write
Change clobber -> overwrite in write
add determine_vconv_from_ctype function
add tests for determinator
add convenience function for accessing velocity convention from a cube
WIP: progress toward appropriate rest frequency conversion
the tests were much harder than the original code...
Small improvements to quickstart example
Improvements to docs
Change rest_frequency to rest_value
Don’t show stokes section until it’s written