feat(pagination): plug into `ngModel` controller

BREAKING CHANGE: Both `pagination` and `pager` are now integrated with `ngModelController`.
 * `page` is replaced from `ng-model`.
 * `on-select-page` is removed since `ng-change` can now be used.

  Before:

  <pagination page="current" on-select-page="changed(page)" ...></pagination>

  After:

  <pagination ng-model="$parent.current" ng-change="$parent.changed()" ...></pagination>