chore(package): update del-cli to version 3.0.0

Closes #6

Author: greenkeeper[bot]

package.json

@@ -32,7 +32,7 @@
   },
   "devDependencies": {
     "cssnano": "^3.9.1",
-    "del-cli": "^0.2.1",
+    "del-cli": "^3.0.0",
     "http-server": "^0.9.0",
     "npmpub": "^3.1.0",
     "postcss-cli": "^2.6.0",