slight mod of gridlex: support @extend .grid in SASS/SCSS
slight mod of gridlex: support @extend .grid in SASS/SCSS

garrett/jekyll-springboard,garrett/jekyll-springboard-community,garrett/jekyll-springboard,garrett/jekyll-springboard,garrett/jekyll-springboard-community,garrett/jekyll-springboard-community,garrett/jekyll-springboard-community,garrett/jekyll-springboard