Add caching around the generated CSS
Add an endpoint for generating a stylesheet from a color
remove the custom background color, we’ll enable customizing the entire color scheme, let’s not confuse things
Refactor how the CSS is generated, temporarily pulls out caching, see #10
Add default color scheme option to the customizer
Set default to real default color (purple)
Rotate hue of highlight color to almost-opposite color, for a nicer contrast