Possibility to use a property for the heigth attriubute
Possibility to use a property for the heigth attriubute

Added a observer to the height attribute., so the height property can be dynamic as well. 

E.G.:
```javascript
export default Ember.ObjectController.extend({
  contentHeight: 200,

  actions: {
    changeHeight(someObject) {
      var height = someObject.doSomeCalculationToGetHeight();
       this.set('contentHeight', heigth)
    }
  }
});
```

`{{summer-note height=controller.contentHeight btnSize=bs-sm content=postContent focus=false header="Example"}}`
vsymguysung/ember-cli-summernote,emoryy/ember-cli-summernote,brett-anderson/ember-cli-summernote,brett-anderson/ember-cli-summernote,wzowee/ember-cli-summernote,wzowee/ember-cli-summernote,Flightlogger/ember-cli-summernote,Flightlogger/ember-cli-summernote,vsymguysung/ember-cli-summernote,emoryy/ember-cli-summernote