[PHP Omnipay library](https://github.com/thephpleague/omnipay-common) port to typescript

### Summary ###

This is the port of  [PHP Omnipay library](https://github.com/thephpleague/omnipay-common) core to use in Node.JS environment
Code itself is written in Typescript 2.7

### Usage ###

Install using `npm install omnipay-js`
```javascript
const { AbstractGateway, AbstractRequest } = require('omnipay-js');
```

Requires NodeJS version **high or equal to 8.6**