Move documentation from gh-pages branch to 'docs' folder

To prepare the migration to 3.0, we need to change the location where the documentation is generated from.
Having a gh-pages branch makes it hard to synchronize the code and the docs. Having a "docs" folder in the repo itself simplifies this.

docs/css/main.scss

@@ -0,0 +1,56 @@
+---
+# Only the main Sass file needs front matter (the dashes are enough)
+---
+@charset "utf-8";
+
+
+
+// Our variables
+$base-font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
+$base-font-size:   16px;
+$base-font-weight: 300;
+$small-font-size:  $base-font-size * 0.875;
+$base-line-height: 1.5;
+
+$spacing-unit:     30px;
+
+$text-color:       #111;
+$background-color: #fdfdfd;
+$brand-color:      #104c81;
+
+$grey-color:       #828282;
+$grey-color-light: lighten($grey-color, 40%);
+$grey-color-very-light: lighten($grey-color, 45%);
+$grey-color-dark:  darken($grey-color, 25%);
+
+// Width of the content area
+$content-width:    800px;
+
+$on-palm:          600px;
+$on-laptop:        800px;
+$on-laptop-big:    1400px;
+
+
+
+// Use media queries like this:
+// @include media-query($on-palm) {
+//     .wrapper {
+//         padding-right: $spacing-unit / 2;
+//         padding-left: $spacing-unit / 2;
+//     }
+// }
+@mixin media-query($device) {
+    @media screen and (max-width: $device) {
+        @content;
+    }
+}
+
+
+
+// Import partials from `sass_dir` (defaults to `_sass`)
+@import
+        "base",
+        "layout",
+        "syntax-highlighting",
+        "index"
+;