#555

Request to merge #555 into the master branch.
I'm a little confused here. I ran a quick test and found that
``` 
im(x+1,y+1) = im.array[y,x].
```
So essentially, the elements of the Image instance are addressed by a column first manner as opposed to row first manner for NumPy arrays and in addition, the indexing begins from 1 and not from 0. I was expecting the relation to be something like 
```
y = (n_rows ) - row_index.
```
It's confusing to me because I still find the 'origin' of the image to be at the topleft corner and the coordinate system is a left-handed one: so if increase y is up, then increasing x becomes left and not right.