wercker.yml with a npm-install step that installs a package globally

wercker.yml

---
box: wercker/nodejs
# Build definition
build:
  # The steps that will be executed on build
  steps:
    # A step that executes `npm install` command
    - npm-install
    # Install karma cli
    - script:
        name: install karma-cli globally
        code: |
          sudo npm install -g karma-cli
    # A step that executes `npm test` command
    - npm-test

    # A custom script step, name value is used in the UI
    # and the code value contains the command that get executed
    - script:
        name: echo nodejs information
        code: |
          echo "node version $(node -v) running"
          echo "npm version $(npm -v) running"