Moved text labels config to attributes and switched $watch to $on

1. All view stuff should be inside html. So I moved text to be configured as attributes in html, and not in controller.
Also classes other config stuff should be refactored too

Now button looks like
```html
<jp-ng-bs-animated-button
    button-default-text="Login"
    button-submitting-text="Loading..."
    button-success-text="Access granted"
    button-error-text="Access denied"></jp-ng-bs-animated-button>
```

2. Replaced $watch variables with more obvious events.

To control behavior we need to emit signal from scope:

```javascript
$scope.$broadcast('submit-button-event', {
    submitting: true
});
```
First argument is object and could have 3 attributes to control status: `submitting`, `success`, `error`