Merge branch 'master' into greenkeeper/eslint-config-prettier-2.7.0

* master:
  remove package-lock
  add yarn lockfile
  install yarn on osx
  update travis to call yarn
  disable npm lockfile generation
  babel-jest has a peerDependency of babel-core
  react-native-maps has a peerDependency of prop-types

Author: hawkrives

.npmrc

@@ -1 +1,2 @@
 save-exact=true
+package-lock=false

.travis.yml

@@ -64,7 +64,7 @@ jobs:
       before_install:
         - npm install -g coveralls
       install:
-        - npm install || npm install
+        - yarn || yarn
       before_script:
         - echo "loglevel=silent" >> .npmrc
         - mkdir -p logs/
@@ -99,7 +99,7 @@ jobs:
       env: [GH_PAGES=yes]
       before_install: skip
       install:
-        - npm install || npm install
+        - yarn || yarn
       before_script: skip
       script: npm run bundle-data
       deploy:
@@ -164,11 +164,14 @@ before_install:
   - nvm install "$TRAVIS_NODE_VERSION"
   - nvm use "$TRAVIS_NODE_VERSION"
   - echo "node -v is now $(node -v)"
+  
+  # travis doesn't install yarn automatically on osx
+  - if [[ $TRAVIS_OS_NAME == "osx" ]]; then brew install yarn --without-node; fi
 
 
 install:
   # install packages (if the first fails, try once more)
-  - npm install || npm install
+  - yarn || yarn
 
   # install fastlane (if at first you don't succeed, try once more)
   - bundle install || bundle install