Compressed render images

@moralismercatus has provided a second set of render images that are compressed much more (smaller file sizes). I put them on a separate branch so we could all review them to see if the compression is too high.

Note: previously the image collection was around 65MB, now it is about 20MB. The latest batch of render images (currently on master branch, and soon to be posted to the Clark website) was around 120MB.

Here is a comparison of the images within the image repository:
https://github.com/millertime-homework/Emergency-Response-images/commit/231c984f9a5ae90c2245590faf0530843836fde4

@arik181, @groveje: can you please let me know what you think? Is it too grainy?