WIP [example] finetuning CaffeNet on Flickr Style data

This example shows how to fine-tune the BVLC-distributed CaffeNet model on a different dataset: [Flickr Style](http://sergeykarayev.com/files/1311.3715v3.pdf), which has style category labels.
The dataset is distributed as a list of URLs with corresponding labels.
Using a script, we will download a small subset of the data, split it into train and val portinos, and use the ImageDataLayer to load images directly from the filesystem.
It'd be nice to define the all-in-one model for train + val like in the ImageNet example.