deps: upgrade http-server and opn

Author: paulirish

package.json

@@ -22,8 +22,8 @@
     "cypress": "^4.0.2",
     "eslint": "^4.19.1",
     "eslint-config-google": "^0.7.1",
-    "http-server": "^0.9.0",
-    "opn-cli": "^3.1.0",
+    "http-server": "^0.12.1",
+    "opn-cli": "^5.0.0",
     "pre-push": "^0.1.1",
     "sw-precache": "^5.2.1"
   },