chore: update Jest to version 22 (#45)

Closes #39

Author: SimenB

.travis.yml

@@ -8,6 +8,7 @@ before_install:
 - curl -o- -L https://yarnpkg.com/install.sh | bash -s -- --version 1.3.2
 - export PATH="$HOME/.yarn/bin:$PATH"
 - yarn global add greenkeeper-lockfile@1
+install: yarn --ignore-engines
 before_script: greenkeeper-lockfile-update
 script:
 - yarn commitlint --from="$TRAVIS_BRANCH" --to="$TRAVIS_COMMIT"

package.json

@@ -27,7 +27,7 @@
     "eslint-config-prettier": "^2.7.0",
     "eslint-plugin-prettier": "^2.3.1",
     "husky": "^0.14.3",
-    "jest": "^21.2.1",
+    "jest": "^22.0.4",
     "lint-staged": "^6.0.0",
     "prettier": "^1.8.1"
   },