Controller Activation Promises (Y080)

https://github.com/johnpapa/angularjs-styleguide/edit/master/README.md
- Resolve start-up logic for a controller in an `activate` function.

_Why?_: Placing start-up logic in a consistent place in the controller makes it easier to locate, more consistent to test, and helps avoid spreading out the activation logic across the controller.

_Why?_: The controller `activate` makes it convenient to re-use the logic for a refresh for the controller/View, keeps the logic together, gets the user to the View faster, makes animations easy on the `ng-view` or `ui-view`, and feels snappier to the user.

Note: If you need to conditionally cancel the route before you start use the controller, use a [route resolve](#style-y081) instead.

``` javascript
/* avoid */
function Avengers(dataservice) {
var vm = this;
vm.avengers = [];
vm.title = 'Avengers';

dataservice.getAvengers().then(function(data) {
vm.avengers = data;
return vm.avengers;
});
}
```

``` javascript
/* recommended */
function Avengers(dataservice) {
var vm = this;
vm.avengers = [];
vm.title = 'Avengers';

activate();

////////////

function activate() {
return dataservice.getAvengers().then(function(data) {
vm.avengers = data;
return vm.avengers;
});
}
}
```