Bump sass-graph@2.2.4 (#1958)

- fixes issues with transitive dependency scss-tokenizer
- allows graph to follow symlinks

package.json

@@ -69,7 +69,7 @@
     "node-gyp": "^3.3.1",
     "npmlog": "^4.0.0",
     "request": "^2.79.0",
-    "sass-graph": "^2.1.1",
+    "sass-graph": "^2.2.4",
     "stdout-stream": "^1.4.0"
   },
   "devDependencies": {