Add prettier as a devDep to get tests passing on CI with npm@2

Author: RyanZim

package.json

@@ -30,6 +30,7 @@
     "eslint-plugin-import": "^2.2.0",
     "npmpub": "^3.0.1",
     "postcss-scss": "^1.0.0",
+    "prettier": "^1.3.1",
     "prettier-eslint-cli": "^3.4.3",
     "sugarss": "^1.0.0"
   },