code: function shebang(data) {
    var matched, script;
  
    if (data && (matched = data.match(/#!\s*([^\s]+)\s*([^\s]+)?/))) {
      script = matched[1].split('/').pop();
      return (script === 'env') ? matched[2] : script;
    }
  
    return null;
  }
docs: Extract normalized shebang command token.
  
  
  Examples:
  
  shebang("#!/usr/bin/ruby") // "ruby"
  
  shebang("#!/usr/bin/env node") // "node"
  
  @param: {String}
  @return {String|null}