Closes #7 (closed)
Creates an /img-cache folder in the application's root, which it then stores JSON blobs of the image data (including the base64-encoded image and its dimensions). This leads to a significant overall speed boost in returning images that have already been generated.
In order to tell if the incoming request has a cached result that would work, this change also needed to put in more robust request-sanitizing logic, such that if a new request comes in, and the only difference to a previous request is the ordering of the parameters, or additional junk parameters have been added, the system can recognize the already-cached result can be used.