Remove dependency on Sass

- Convert *.sass files to vanilla CSS
- Start using CSS variables
- Add PHP minifier

libs/path-converter/src/ConverterInterface.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace MatthiasMullie\PathConverter;
+
+/**
+ * Convert file paths.
+ *
+ * Please report bugs on https://github.com/matthiasmullie/path-converter/issues
+ *
+ * @author Matthias Mullie <pathconverter@mullie.eu>
+ * @copyright Copyright (c) 2015, Matthias Mullie. All rights reserved
+ * @license MIT License
+ */
+interface ConverterInterface
+{
+    /**
+     * Convert file paths.
+     *
+     * @param string $path The path to be converted
+     *
+     * @return string The new path
+     */
+    public function convert($path);
+}