fix: install dependencies in example travis

Author: roggervalf

.gitignore

@@ -10,5 +10,5 @@
 
 # files
 node_modules/
-example/dist/
 dist/
+build/

.travis.yml

@@ -20,6 +20,7 @@ script:
   - export GIT_PUBLISH_URL=https://${GH_TOKEN}@github.com/wwayne/react-tooltip.git
   - if [ "$TRAVIS_BRANCH" == "master" ] && [ "$TRAVIS_PULL_REQUEST" = "false" ]; then yarn gh-pages -- --repo ${GIT_PUBLISH_URL}; fi
   - cd example
+  - yarn
   - yarn build
 
 deploy: