Documentation: expanded should be a boolean instead of a string

[Bargs]

The current readme shows the following code for adding an expanding slider to your template:

{{loading-slider isLoading=loading expanding="true" color=hexColorsArray}}

Because the expanding property is listed in classNameBindings, the component's element is given a class matching the string value of this property: true.

To get a class value of expanding as expected, I had to pass expanding's value as a boolean instead of a string:

{{loading-slider isLoading=loading expanding=true color=hexColorsArray}}

Using Ember 1.10.0