Material theme of ember-power-select

Hi again.

I also tried to use it for material theme of ember-power-select, in my ember-cli-build.js I have:

``` javascript
'ember-power-select': {
theme: 'material'
}
```

and when I use your component out of the box, I do not see any arrow/cross/loading icons on the right side.

Is it me doing something wrong or there is no support for material theme of ember-power-select ?

Start with the ember-cli-build.js configuration shown in the issue and reproduce the component with ember-power-select's material theme enabled. Trace the material-theme integration for the arrow, cross, and loading icons; done means those icons appear on the right side when the component is used with that configuration.

Written by the indexing model from the issue text.