Feature Request: Semantic Option

[davidpanzarella]

I'm liking your grid system quite a bit, but would love to see an option to not have to put extra classes into the DOM if possible. Sort of the same thing that Bootstrap does currently with makeContainer(), makeRow(), etc. This particularly becomes useful as you can't use @extend's in Media Queries nor can you do stuff like this:

.header {
  background-color: #fff;

  &__inner {
    @extend .grid;
    @extend .container;
  }

  &__logo {
    @extend .col;
  }

  &__nav {
    @extend .col;
  }
}