Fixes `AttributeError: reader`
Fixes `AttributeError: reader`

I get the error

Exception ignored in: <bound method VideoFileClip.__del__ of <moviepy.video.io.VideoFileClip.VideoFileClip object at 0x10d347d30>>
Traceback (most recent call last):
File "/anaconda/lib/python3.5/site-packages/moviepy/video/io/VideoFileClip.py", line 89, in __del__
    del self.reader
AttributeError: reader

The error doesn't actually crash the program, but we don't need it
ssteo/moviepy,Zulko/moviepy,kerstin/moviepy