Add a option to edit CSS files through a text area in the admin section

Issue Summary

First, awesome module. Just what I was looking for and needed! I had created a custom theme for a series of clients (political candidates) as part of a special deal with the local party, but a few clients were wanting small CSS customizations. Now I know this exists I'll be using this all the time. Imagine a bare bones Zen subteme used on all the sites in a multisite installation, each with their own site specific CSS that totally customizes the design for the site. That's fantastic! Kudos.

Feature request. Why not have a configuration screen where we can edit the CSS file directly. Upon submit it would write out the css file to the appropriate directory, with the correct name, etc., which it could get by looking up the current theme name and files directory. Could also have the config component maybe validate the CSS, maybe optionally code format/tidy, if you wanted to go hog wild. This could be a total winner of a little module!