Update step_02.ngdoc

Request Type: feature

How to reproduce: Not a bug.  Simply suggestion as to how to improve the clarity of the tutorial.

Component(s): 

Impact: small

Complexity: small

This issue is related to: 

**Detailed Description:**

The issue was raised only as a suggestion as to how to make the Tutorial clearer.  I suspect this form is not really appropriate for that purpose.

**Other Comments:**

The changes suggested above put things in a better sequence and in terms that are more easily understood by a new-comer.  Firstly, it is best to introduce the concept of "Scope" before talking about it.  That's why I have moved it up.

Next, with the present writing I found myself lost for a moment.  Because of my background with the Play Framework I went looking for a folder called controllers.  In the Play Framework, there are three folder within the app folder.  These are views, controllers and models.

Instead, with angularjs, controllers are located in app/js/controllers.js, a file, not a folder.