Adds minification to vanilla CSS and HTML

[kennethormandy]

• Adds consistent CSS minification to vanilla CSS files
• Adds consistent minification to HTML files

The HTML one still has one failing test I’m not sure about:

  1) render(path, callback) plain should fire callback when:
     AssertionError: expected '<h1>Just a plain old html file.</h1>' to not exist
    at test/render.js:129:20
    at Object.render (lib/terraform.js:143:11)
    at Context.<anonymous> (test/render.js:128:12)

[lunelson]

@kennethormandy is there any chance minification is, or could be, dependent on the ENVIRONMENT variable? I use Harp for prototyping and my HTML output is often copy-pasted over to PHP development, so currently I've disabled minification in my own fork but a development/production flag would be cool cause obviously server-side it should be minified