Added css_minify_tag and js_minify_tag

Added css_minify_tag and js_minify_tag, which in conjunction with the new theme config file will automagically minify your assets!

Update May 6: The minified assets don’t currently work with relative asset paths. We’re working on this and will update this when that is fixed.

Update May 6: Fixed! The minification of CSS files will now automatically rewrite the relative file paths to absolute. Contact support if you have any trouble with this feature.

As always, minifying javascript can cause problems for incorrectly formatted javascript (ie, missing semicolons). While the CSS minify is fairly straightforward, check your javascript console after switching to the minified javascript to make sure its working at intended.