Python wrapper polish

This is a work in progress for

- [x] formatting to convert images to Caffe format for deployment, or convert Caffe images back to normal images for viewing
- [ ] batching for feeding inputs to the net with padding as needed
- [ ] python exceptions instead of library crashes
- [ ] a more complete wrapper example that shows how image formatting, computing the forward pass, and reading off predictions works
- [ ] properly separate responsibilities between the pycaffe wrapper, the imagenet wrapper example (wrapper.py) and detection example (detector.py)