Documentation update?

Hi there. I have spent a little while debugging why my chart wasn't working. I was tipped to the final solution but Stack Exchange.

It was to wrap my component in a `div`. The SE answer mentioned setting a height which I've found wasn't necessary.

period-graph.component.hbs
*Doesn't work*
```handlebars
{{ember-chart type="line" data=model.chartdata options=model.chartoptions}}
```
*Does work*
```handlebars

```
I know that this is probably outside the remit of this addon. And I'm not sure why this is the case. But it means that the README sample doesn't work out of the box for components.

The first thing that twigged me to it, which resulted in a productive Google search, was turning off responsive.

```javascript
let options = { responsive: false };
```