Bump node-sass to ^3.8.0

Author: cvrebert

package.json

@@ -26,7 +26,7 @@
     "url": "https://github.com/twbs/bootstrap-sass/issues"
   },
   "devDependencies": {
-    "node-sass": "~3.7.0",
+    "node-sass": "^3.8.0",
     "mincer": "~1.4.0",
     "ejs": "~2.4.2"
   },