dot-rendered images transparent and shadows added

[chadmiller-saq]

Dot used to write opaque white backgrounds. Normally okay until night falls.

Now, write transparent images.

This sucks because the foreground is still dark.

We instead use CSS drop-shadows to draw a text color around the alpha edges, thereby making black-on-black, actually black-over-white-on-black.

[chadmiller-saq]

Previously

[chadmiller-saq]

This is going to conflict with #21, but the resolution should be obvious.