Setup coverage reporting with codecov.

Author: ghengeveld

.gitignore

@@ -1,2 +1,3 @@
 lib/
 node_modules/
+coverage/

.travis.yml

@@ -4,3 +4,5 @@ node_js:
 cache:
   directories:
     - node_modules
+after_success:
+  - bash <(curl -s https://codecov.io/bash) -e TRAVIS_NODE_VERSION

package.json

@@ -39,5 +39,9 @@
     "react": "16.4.2",
     "react-dom": "16.4.2",
     "react-testing-library": "5.0.0"
+  },
+  "jest": {
+    "coverageDirectory": "./coverage/",
+    "collectCoverage": true
   }
 }