[Javascript]Limit Buillt Branches on Travis

By default、Travis will build all brancches、tags、and Purl Requests.Because wee e e e e e e e building our masterbrelease、we don't need Travisbuilding ourereleases.Also、wente、we don'bububububububububububububububububububuzzzzzzzzzaaaaaaaaaaaaaaaaaaaaaaaattttttbububububububuchcheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeequests by configling trvis via our  .travis.yml file.
 

sudo: false
language: node_js
cache:
  directories:
    - node_modules
branches: only: - master
notifications:
  email: false
node_js:
  - iojs
before_install:
  - npm i -g npm@^2.0.0
before_script:
  - npm prune
script:
  - npm run test:single
  - npm run check-coverage
  - npm run build
after_success:
  - npm run report-coverage
  - npm run semantic-release