Acts weird when using with webpack

When bundling with webpack.
```js
// import omit from 'omit.js'; <== works
// const omit = require('omit.js').default; <== works
// const omit = require('omit.js'); <== does NOT work
console.log(omit({ foo: 'foo', bar: 'bar' }, ['bar']));
```
May just want to better support commonjs - if a library uses this package internally and requires it via require('omit.js') - and then webpack is used to bundle the lib omit will always be undefined.

I ran into this issue when trying to bundle [cabin](https://github.com/cabinjs/axe) with webpack and omit would always be undefined. The author switched to lodash/omit to remedy the issue.

Start by reproducing the webpack bundle behavior from the CommonJS examples in the issue, comparing require('omit.js') with require('omit.js').default and the ES module import. Inspect the omit.js package entry points and bundler configuration, then verify that the direct CommonJS require exposes the omit function when bundled with webpack.

Written by the indexing model from the issue text.