lib/docs/retriever.js
function getMainFieldAsArray(main) {
  if( main.constructor === Array ) {
    return main;
  } else {
    if( fs.existsSync(main) ) {
      return [main];
    } else if( fs.existsSync(main+'.js') ) {
      return [main+'.js'];
    } else {
      return [];
    }
  }
}
function getMainFieldAsArray(main) {
  if( main.constructor === Array ) {
    return main;
  } else {
    if( fs.existsSync(main) ) {
      return [main];
    } else if( fs.existsSync(main+'.js') ) {
      return [main+'.js'];
    } else {
      return [];
    }
  }
}
Returns an Array of the files mentioned in a 'main' field
If the value is noted without '.js' at the end, it is appended.