Material-ui: [Lab] Slider component is not working in IE11

[sodik82]

Expected Behavior

Slider can change its value e.g. by clicking.

Current Behavior

Slider onChange callback value is NaN. As I was able to track down, percentage computation does not work.

Steps to Reproduce (for bugs)

1. Open https://material-ui.com/lab/slider/ in IE11
2. Try to click on slider to change.

Your Environment

| Tech | Version |
|--------------|---------|
| Material-UI | v1.1.0 + material-ui/lab@^1.0.0-alpha.3 |
| React | 16.4.0 |
| browser | IE 11.0.9600 , Win7 |

[mbrookes]

@epodivilov Are you okay to take a look at this?

[epodivilov]

Fixed in this PR