Unity standard Assets is recieveing error

Replace

 rigidbody2D

with

 GetComponent<Rigidbody2D>()

example

 GetComponent<Rigidbody2D>().velocity = transform.up * speed;

Alternatively you can cache the components like before by storing the component in a variable.

 Rigidbody2D body;
 
 void Start()
 {
   body = GetComponent<Rigidbody2D>();
 }

If performance isn't an issue Unity will automatically do this via the API updater. You can find it in the menu bar at Assets -> Run API Updater

This is part of a change targeting multiple accessors:

Removed quick property accessors, like .rigidBody, .rigidbody2D, .camera, .light, .animation, .constantForce, .renderer, .audio, .networkView, .guiTexture, .collider, .collider2D, .particleSystem, .particleEmitter, .guiText, .hingeJoint for modularization. Instead, use GetComponent to get references.

Read more about it here: http://blogs.unity3d.com/2014/06/23/unity5-api-changes-automatic-script-updating/

If you are new to Unity there is a set of basic scripting tutorials including one on GetComponent usage here.