Compress images

Compress images using
[ImageOptim](https://github.com/pornel/ImageOptim) version 1.4.4
Convert assorted images to limited-palette PNG

Convert images that don't have very many visibly different colors to
limited-palette PNGs containing a maximum of 256 different colors. This
reduces file size tremendously.
Convert to limited-palette PNG

Convert `data/news/*.png` to limited-palette PNGs containing a maximum
of 256 different colors. This reduces file size tremendously.
Merge pull request #6 from pathawks/master

WEB: Compress image files to make site speedier