Feature/add refresh access token method to api client (#88)
Feature/add refresh access token method to api client (#88)

* Split up method so that we can re-use the logic to retrieve a new access token using a refresh token instead of authorization code

* Removed note about not being allowed to edit the ApiClient class

* Putting the code in the right array index

* Cleaned up imports

* Removed blank line
docusign/docusign-php-client