Better CSS file structure

[daviddarnes]

Similar to Alembic, Garth needs to be easy to style. The best way would be to have the following file structure:

_sass/
  sassline-base/
  _flex.scss
  _normalize.scss
  _sassline-base.scss
  _settings.scss
  _theme.scss
  _garth.scss
assets/
  styles.scss

garth.scss will import all the theme related styles, including _theme.scss. Then in turn assets/styles.scss will import garth. This means all theme related styles are in one place and the theme user only has to import one file if they wish to add their own custom styles.