Reorganizes asset file structure

Separates assets into
- Source assets: `assets`
- Compiled assets: `dist`

Edits assets.php to reflect changes

Removes '.min' from filenames

Fixes:
- removes 'clean' from build step.

lib/init.php

@@ -28,7 +28,7 @@ function roots_setup() {
   add_theme_support('html5', array('caption', 'comment-form', 'comment-list'));
 
   // Tell the TinyMCE editor to use a custom stylesheet
-  add_editor_style('/assets/dist/css/editor-style.css');
+  add_editor_style('/dist/css/editor-style.css');
 }
 add_action('after_setup_theme', 'roots_setup');