Bug fix for enlarging bounding boxes that is beyond the image boundary

[TiankangXie]

Problem: sometimes bounding boxes are beyond image boundary. Some bugs (negative values) were seen during Rescale processes.
Details: Calling detector.process_image on one of the CK+ images (original size 200x200) raises the following error: RuntimeError: Input and output sizes should be greater than 0, but got input (H: 0, W: 188) output (H: 0, W: 224) From the error trace it is evident that the Rescale function is not working properly. Need to investigate on this issue.

[TiankangXie]

Apparently it is an issue of placing top & bottom boundary of the image in reverse order. Bug is fixed and will be released in the next version