emoji gives wrong padding

I expected emojies to work, but ✅ for example gets extra padding:

```
┌─────────────┬───┬──────────────┐
│ First value │ ✅ │ Second value │
└─────────────┴───┴──────────────┘
```

Same result in Mac Terminal, VSCode terminal and iTerm.

Example code:

```js
var Table = require('cli-table');

var table = new Table()
table.push(['First value', '✅', 'Second value'])
console.log(table.toString());
```