Compile sprites to utf8 version of SVG instead of Base64

Because Base64 is bigger and SVGs are better at getting gzipped.

Gains: 8 KB just for the global sprite. So even more overall if you include the commercial sprite.

```bash
# Normal
105700 _global-icons-svg BASE 64.scss
85398 _global-icons-svg UTF8.scss

# Gzipped
28053  _global-icons-svg BASE64.scss.gz
20714 _global-icons-svg UTF8.scss.gz
```

![ ](http://media.giphy.com/media/qzYBlG969xs6k/giphy.gif)