Integration of astropy.units in sunpy codebase

Attempt to integrate the astropy.units into sunpy. Every function that were taking or giving a quantity now must have astropy quantity associated with them. Please tell me if I have made mistakes anywhere, or if it could be done in better way, I will make changes! 
Thank you!   
Also, would not be a way to test whether the quantity input belongs to spectral units? I mean, if I put a '5 kg' as an input this should raise an error... right?