Reproducing ECCV 18 plots

[una-dinosauria]

This is a meta-issue of https://github.com/una-dinosauria/Rayuela.jl/issues/26

We want to make it easy for people to reproduce our main results. These are the things that are missing for push-button reproducibility.

• [x] Make sure code works on Julia 1.0
• [ ] Add a flag to use the GPU or use CPU only
• [ ] Expose flag to choose codebook update method for LSQ/LSQ++
• [ ] Homogeneize API of GPU and CPU methods (currently they are methods with different names)
• [ ] Make demo code return and save time spent (currently only returns and saves results)
• [ ] Add plotting code