Implement TestDataBuilder

[bajtos]

Usage:

// The context object to hold the created models.   
// You can use `this` in mocha test instead.        
var context = {};                                   

var ref = TestDataBuilder.ref;                      
new TestDataBuilder()                               
  .define('application', Application, {             
    pushSettings: { stub: { } }                     
  })                                                
  .define('device', Device, {                       
     appId: ref('application.id'),                  
     deviceType: 'android'                          
  })                                                
  .define('notification', Notification)             
  .buildTo(context, function(err) {                 
    // test models are available as                 
    //   context.application                        
    //   context.device                             
    //   context.notification                       
  });                                               

/to: @raymondfeng @ritch Please review.
/cc: @rmg @Schoonology

Related discussions in loopback-push-notification: what values to use as default, what types to support.

[slnode]

Test PASSed. To trigger a build add comment - ".test\W+please"
Refer to this link for build results: http://ci.strongloop.com/job/loopback-testing/10/

[slnode]

Test PASSed. To trigger a build add comment - ".test\W+please"
Refer to this link for build results: http://ci.strongloop.com/job/loopback-testing/11/

[ritch]

What is ref used for?

Edit - I see now.

[ritch]

Can ref be available as this.ref() in define callbacks?

[ritch]

Overall LGTM

[bajtos]

Can ref be available as this.ref() in define callbacks?

No, as there are not define callbacks. define accepts objects only.