Implements in-memory loading of images

[soumith]

The following now works:

with open('chicago.jpg', 'rb') as f:
   img_bytes = f.read()
img = accimage.Image(img_bytes)

Fixes #2 cc: @vadimkantorov

[vadimkantorov]

That issue dates a bit back :)

[willprice]

I'm not sure this is going to work as strings in python 2 were bytes by default: b'hi' == 'hi'. This is why travis is failing at the moment. I'm not sure what we should do--drop python 2 support completely? (Although if torchvision is still supporting 2, so should accimage). If we need to support 2, perhaps we could ask for a bytesio object?

[soumith]

I'll fix it, i think I can make the in-memory option be a kwarg-only option probably.

[soumith]

i am closing this and calling work bankruptcy :)