fix(package): adding missing dependencies for travis

Author: Halceyon

package.json

@@ -53,6 +53,7 @@
     "eslint-config-airbnb-base": "^12.1.0",
     "eslint-plugin-import": "^2.2.0",
     "istanbul": "^1.1.0-alpha.1",
+    "json-stable-stringify": "^1.0.1",
     "mocha": "^5.0.1",
     "parse-json": "^4.0.0",
     "rollup": "^0.56.2",