Add info on the Sandbox env

Author: faktas2

README.rst

@@ -44,6 +44,13 @@ constructors take your MaxMind account ID and license key:
     >>> client = Client(42, 'licensekey')
     >>> async_client = AsyncClient(42, 'licensekey')
 
+To use the Sandbox web service instead of the production web service,
+you can provide the host argument:
+
+.. code-block:: pycon
+
+$mf = new MinFraud(1, 'ABCD567890', [ 'host' => 'sandbox.maxmind.com' ]);
+
 Score, Insights and Factors Usage
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 

minfraud/webservice.py

@@ -455,6 +455,11 @@ def __init__(
         :param license_key: Your MaxMind license key
         :type license_key: str
         :param host: The host to use when connecting to the web service.
+          By default, the client connects to the production host. However,
+          during testing and development, you can set this option to
+          'sandbox.maxmind.com' to use the Sandbox environment's host. The
+          sandbox allows you to experiment with the API without affecting your
+          production data.
         :type host: str
         :param locales: A tuple of locale codes to use in name property
         :type locales: tuple[str]