added .travis.yml file

[manjula-dube]

Adding travis file

[nitish24p]

You can add more commands https://docs.travis-ci.com/user/customizing-the-build/

language: node_js

node_js:
  - 6
before_script:
  - npm install # or install only eslint plugins needed

script:
  - npm run eslint # eslint  in scripts of package.json

cache:
  apt: true
  directories:
    - node_module