feat(uibootstrap-modal): add basic modal service and template when using uibootstrap

Changes: (only if ui-bootstrap is selected)
- add `client/components/modal` folder
- modal folder contains service, markup template, and stylesheet
- modal service is intended to be extended, comes with `Modal.confirm.delete()` method
- admin and main page will both use `Modal.confirm.delete()`

Todo:
- possibly extend the modal service to include a basic alert class?
- review code for cleanliness and correctness
- write test for `Modal` service?
That is correct @ethanve, The `delete(callback)` method returns a function that will open a modal with it's callback bound to the callback provided to the delete method. The use cases are when you would like to create references in your controllers to the modal confirm callback, and then provide a simple modal launching function to bind to an `ng-click` like so:
**controller.js**
```javascript
...
$scope.delete = Modal.confirm.delete(function(user) {
  /* Delete user here */
});
...
```

Then in your markup you can do stuff like:
```html
...
<div ng-repeat="user in users">
  <button ng-click="delete(user)">Delete {{user.name}}</button>
</div>
...
```

That way you won't need to pass the callback in your markup, it will already be bound to the proper action, as defined in the controller. The `user` that is passed in by the `ng-click` is the same user the callback will receive, as a matter of fact, you can pass any amount of arguments and they will be passed to your callback. As an added feature, we've bound the callback's `this` context to the `$event` object created when the modal's confirm button was clicked. That should provide you with several ways to get the right hooks you need, hopefully...

Hope this clears things up for you :)