Use npm instead of yarn

.prettierrc

@@ -0,0 +1,3 @@
+{
+  "singleQuote": false
+}

.travis.yml

@@ -1,10 +1,10 @@
 language: node_js
-cache: yarn
+cache: npm
 services:
   - redis-server
 script:
-  - yarn test --silent
+  - npm test
-  - yarn build
+  - npm run build
 deploy:
   provider: heroku
   skip_cleanup: true

jest.config.js

@@ -4,5 +4,6 @@ module.exports = {
   },
   setupTestFrameworkScriptFile:
     "<rootDir>/modules/__tests__/setupTestFramework.js",
-  testMatch: ["**/__tests__/*-test.js"]
+  testMatch: ["**/__tests__/*-test.js"],
+  testURL: "http://localhost/"
 };