add support for progressive JPEG emulation

This adds support for Progressive JPEG emulation to add even more terribleness.  The only real issue with this setup is we can't pull the images via getElementsByTagName() since that gets a live collection that would grow infinitely each time a new blurred image is created.  I used querySelectorAll('img:not([class="progessiveJPEGemulator"])') instead only when the progressiveJPEG parameter is set to true.