'Solves the problem with division where the result isn\'t integer.
For example, when dividing a 100px image in 3 parts, the collage
division should be like 33px + 33px + 34px = 100px. In this case,
slice_size is 33px and major_slice_size is 34px.'

def divide_size(self, size, parts):

    slice_size = (size / float(parts))
    major_slice_size = math.ceil(slice_size)
    slice_size = math.floor(slice_size)
    return (int(slice_size), int(major_slice_size))
