fixed "sign up for Windows Azure" link

Author: christothes

README.md

@@ -46,7 +46,7 @@ Getting started with the sample is easy. It is configured to run out of the box
 
 ### Step 1: Register a Windows Azure AD Tenant
 
-To use this sample you will need a Windows Azure Active Directory Tenant. If you're not sure what a tenant is or how you would get one, read [What is a Windows Azure AD tenant](http://technet.microsoft.com/library/jj573650.aspx)? or [Sign up for Windows Azure as an organization](http://www.windowsazure.com/en-us/manage/services/identity/organizational-account/). These docs should get you started on your way to using Windows Azure AD.
+To use this sample you will need a Windows Azure Active Directory Tenant. If you're not sure what a tenant is or how you would get one, read [What is a Windows Azure AD tenant](http://technet.microsoft.com/library/jj573650.aspx)? or [Sign up for Windows Azure as an organization](http://azure.microsoft.com/en-us/documentation/articles/sign-up-organization/). These docs should get you started on your way to using Windows Azure AD.
 
 ### Step 2: Register your Web API with your Windows Azure AD Tenant