code: function getSrc(file) {
    const encodedContents = new Buffer(file.contents).toString('base64')
    return `src:url(data:${mime.lookup(file.path)};charset=utf-8;base64,${encodedContents});`
  }
docs: Convert file contents to a Base64-encoded data: URL.
  @param  {Object} file File object.
  @return {String}      Base64-encoded contents inside a `data:` URL.