gulp and file structure overhaul

new gulp setup
including new npm packages
new file structure
moved all development files to source/
used files are in build/ now

source/style/functions/_shade.scss

@@ -0,0 +1,24 @@
+@charset "UTF-8";
+
+// Mixes a color with black.
+//
+// @param {Color} $color
+//
+// @param {Number (Percentage)} $percent
+//   The amount of black to be mixed in.
+//
+// @example scss - Usage
+//   .element {
+//     background-color: shade(#0c85ff, 60%);
+//   }
+//
+// @example css - CSS Output
+//   .element {
+//     background-color: #074f99;
+//   }
+//
+// @return {Color}
+
+@function shade($color, $percent) {
+  @return mix(#000, $color, $percent);
+}