Additional tests for sunpy.map.map

Currently, I also need to add tests for the rotate method. But I get an `ImportError` while I use that. Any solutions for this?

```p
>>> from sunpy import *
>>> m = sunpy.make_map(sunpy.AIA_171_IMAGE)
>>> m.peek()
<matplotlib.figure.Figure object at 0xacea46c>
>>> n = m.rotate(0.5)
"The C extension sunpy.image.Crotate is not 
installed, falling back to the interpolation='spline' of order=3
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "sunpy/map/map.py", line 852, in rotate
    interp_type = Crotate.BICUBIC
NameError: global name 'Crotate' is not defined
>>> import sunpy.image.Crotate as Crotate
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named Crotate
>>>
```