[AngularJS] Basic Concepts

Here are the basic concepts of Angularjs, these concepts are barely well documented by the officials.

1. angular.config only accepts providers
2. Every service and factory are the instances of the providers
   
   e.g.
   

   angular.module('myApp')
     .service('FooService', function(){
       //...etc
     })
     .config(function(FooServiceProvider){
       //...etc
     });
   
   
   

   Reference: http://stackoverflow.com/questions/17485900/injecting-dependencies-in-config-modules-angularjs