Image size and HTTP requests savings report

Motivation

As the aim of SmartSprites is to decrease the size of the assets downloaded from the server and the number of HTTP requests, it would be good to print some information about the savings after processing completes.

Implementation

After SmartSprites completes processing, it should print out an INFO-level message containing the following information:

• number of sprites created
• for each sprite: size of the sprite, total size of the sprite's images, download size saving ((imagesSize - spriteSize)/imagesSize)
• total download size savings ((allImagesSize - allSpritesSize + allSpriteCssSize)/(allImageSize + allOriginalCssSize))
• total number of requests saved (numberOfImages - numberOfSprites)