Resize a lot of images

Implementing the amazing library: https://github.com/nfnt/resize in order to use it with a folder filled with images.

how to use it:

1. clone this repo.
2. Put some jpg images inside the img folder.
3. run it.
4. Get the images on the results folder.

#To do: [ ] Get specs from a json file. [ ] Support more formats. [ ] Document it better...