undefined foo in `import foo from 'bar';` conversion

Hi! Thanks for this plugin.

I'm encountering an issue in the conversion of var foo = require('bar'); to import foo from 'bar'; where foo is undefined in the following specific case:

// bar.js
exports.hello1 = function() { ... }
exports.hello2 = function() { ... }

// foo.js
const foo = require('./bar');

these get converted to:

export var hello1 = function() { ... }
export var hello2 = function() { ... }

and:

import foo from './bar';
// Here's the issue: foo is undefined as it expects bar module to have a default export

Expected output should be (in that particular case):

import * as foo from './bar';