Improvements to examples/classification/

[lukeyeager]

This lets you classify multiple images without needing to edit the example at all. I found it useful while investigating #536.

• Allow multiple input image files
• Expose batch_size as an option

[lukeyeager]

FYI, you can use a command like this to:

1. Read a list of images from a text file
2. Strip off any label information at the end of each line
3. Pass the image files as command-line arguments to use_archive.py:

cat list-of-images.txt | awk '{print $1}' | \
    xargs ./use_archive.py 20160129-133556-a640_epoch_3.0.tar.gz --batch-size=10