Design preliminary layout for refills

[creuter]

This adds a temporary placeholder refill to use while we figure out layout and how to display its code. It adds middleman-sprockets for asset packaging.

[whmii]

I might change that JS to be something like the following so that if users want to change it later, it's a little easier to add to modularly:

var expandComponent = function(){
  var $button = $("button");
  $menu = $button.siblings(".example");

  var toggleComponent = function() {
    $menu.toggleClass("is-open");
  };

  $menu.click(toggleComponent);
};
$(expandComponent);

p.s. I didn't test this code : P

[whmii]

Generally super pumped to see movement on this 👍

[creuter]

Thanks! Updated based on feedback.

• I've opted to add a separate variables partial that's imported after all of the refills, so those won't inadvertently be affected by custom changes.
• Site related styling is now in its own directory, to make the distinction clearer