Install lessc on wercker

wercker.yml

box: wercker/python
  build:
    steps:
      - script:
        name: "install lessc with sudo"
        code: |-
          curl https://npmjs.org/install.sh | sudo bash
          sudo npm install less -g
      - script:
        name: "install lessc locally"
          curl https://npmjs.org/install.sh | npm_config_prefix=~/local sh
          ~/local/bin/npm install less