clearSelection() with no arguments has no effect?

Visit: http://esri.github.io/cedar/examples/bar.html

Open the browser javascript console, and execute the following line of code (the first bar in the first example chart should become highlighted, as expected):

```js
chart.select({key: "Type", value: "Middle School"});
```

Now try this:

```js
chart.clearSelection(); // or chart.clearSelection({});
```

This is expected to clear all selected items. Actual results are that the chart remains unchanged.

I've found that if I retain the key/value object originally provided to the `select()` method, I can pass this again to the `clearSelection()` method, but that only works to clear individually selected items, and it would be more convenient to have clearSelection() (with no arguments) remove all selected items (as documented).

This issue exists in v0.9.2 - not sure about 1.x