Losslessly compress images.

Before: 946 KB (969.290 bytes)
After:  743 KB (761.347 bytes)
Compress lesscss.jpg with kraken.io.

Savings 618 bytes.
Convert images to 8-bit.

Before: 743 KB (761.347 bytes)
After:  405 KB (415.638 bytes)
package.json: use the https repo URL.