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!   
`true_long` is in degrees and only the same units can be subtracted so I multiplied `u.deg` there.
Indeed right. No need to convert to radians if its in degrees. I will change them accordingly wherever `np.radians(..)` isn't required!