if-env/.travis.yml

Simplify npm scripts with "if-env ... && npm run this || npm run that"

sudo: false
language: node_js
cache:
  directories:
    - node_modules
notifications:
  email: false
node_js:
  - "5"
  - "4"
  - "0.12"
before_script:
  - npm prune
branches:
  except:
    - "/^v\\d+\\.\\d+\\.\\d+$/"