Add tutorial: Create a section of how to test it.

[ignacio-chiazzo]

Use the example in the readme and add a tutorial on how to use it.

Example:

   Create a business account by visiting ....


   set the following variables: 
   ACCESS_TOKEN
   FROM_BUSINESS_NUMBER
   TO_PHONE_NUMBER


   # show some examples of how to use it to validate that the response is received.

We can even use this tutorial as an integration test with a real device, of course, the numbers should be opaque in the tutorial.