Added "bypassCache" option to let the browser cache the images.

[eguaj]

By default, image's URLs are prefixed with a timestamp which prevent the browser from caching the image.

Setting "bypassCache: false" disable this prefix, and allow the browser to cache the images and do If-Modified-Since requests instead of fetching the whole image.

[larrybotha]

I'm glad this has been proposed.

Cache busting should be disabled by default, however. I'm not sure of the use case for loading every image every page load, but allowing images to cache by default would improve user experience. Cache busting should be enabled only when needed.

[eternal-sorrow]

Is this likely to be merged? Would be good to have the possibility to disable this feature.