Remove polyfill code for old node JS versions

Author: rjmunro

lib/fs-helpers.js

@@ -42,18 +42,14 @@ var helpers = {
      *
      * @param {String} path
      */
-    exists: typeof fs.access === 'function' ?
-        function (path) {
-            try {
-                fs.accessSync(path);
-                return true;
-            } catch (err) {
-                return false;
-            }
-        } :
-        function (path) {
-            return fs.existsSync(path);
-        },
+    exists: function (path) {
+        try {
+            fs.accessSync(path);
+            return true;
+        } catch (err) {
+            return false;
+        }
+    },
 
     /**
      * @param {String} path