build(npm): update to mock-fs@3.6.0

tools/broccoli/broccoli-flatten.spec.ts

@@ -1,11 +1,6 @@
 /// <reference path="../typings/node/node.d.ts" />
 /// <reference path="../typings/jasmine/jasmine.d.ts" />
 
-console.warn(
-    "Skipping all tests in broccoli-flatten.spec.ts because they require mock-fs which is currently incompatible with node 4.x. See: https://github.com/tschaub/mock-fs/issues/59");
-
-
-/*
 let mockfs = require('mock-fs');
 import fs = require('fs');
 import path = require('path');
@@ -79,4 +74,3 @@ describe('Flatten', () => {
                       path.sep + "file-1.txt'");
   });
 });
-*/