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!   
With the use of `quantities` this function is not neede anymore, you can delete it.
```python
>>> from astropy import units as u
>>> from astropy.coordinate import Angle
>>> angle_0 = Angle(35.2324, u.deg)
>>> angle_0.hms
 hms_tuple(h=2.0, m=20.0, s=55.776000000001318)
>>> angle_0.to_string(sep='hms')
 u'35h13m56.64s'
```