Add yarn stuff to travis file

Author: JamieDixon

.travis.yml

@@ -8,6 +8,10 @@ cache:
   - node_modules
   - packages/create-react-app/node_modules
   - packages/react-scripts/node_modules
+before_install:
+ - rm -rf ~/.yarn
+ - curl -o- -L https://yarnpkg.com/install.sh | bash
+ - export PATH=$HOME/.yarn/bin:$PATH
 install: true
 script:
  - 'if [ $TEST_SUITE = "simple" ]; then tasks/e2e-simple.sh; fi'