EditableInput increase/decrease percentage by 1% when arrow up/down 
First of all, this is an amazing open source project, and the API is incredible to work with. When I wanted to create this issue I realized how small this world is when I saw it is maintained by @casesandberg — explains the high quality bar.

When using `ChromePicker`, the Saturation and Lightness controls in the HSL view  don’t respond to arrow up/down, most likely because the value is a percentage.

I think this part confirms my thinking: https://github.com/casesandberg/react-color/blob/master/src/components/common/EditableInput.js#L45

```javascript
 handleKeyDown = (e) => {
    const number = Number(e.target.value)
    if (!isNaN(number)) {
```

I am proposing the following solution, which I still need to test:

```javascript
 handleKeyDown = (e) => {
    const number = Number(e.target.value.replace(/%/g, ''))
    if (!isNaN(number)) {
```

