Add Sandbox information

Author: faktas2

README.md

@@ -48,6 +48,12 @@ arguments. For example:
 WebServiceClient client = new WebServiceClient.Builder(6, "ABCD567890").build();
 ```
 
+If you would like to use the Sandbox environment, you can use the `host` method 
+that belongs to the Bulder. For example,
+```java
+WebServiceClient.Builder.host("sandbox.maxmind.com")
+```
+
 Then create a new `Transaction` object. This represents the transaction that
 you are sending to minFraud. The class is instantiated using an inner builder
 class, `Transaction.Builder`. Each builder method takes a corresponding

src/main/java/com/maxmind/minfraud/WebServiceClient.java

@@ -138,6 +138,11 @@ public WebServiceClient.Builder disableHttps() {
 
         /**
          * @param val The host to use.
+         * 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.
          * @return Builder object
          */
         public WebServiceClient.Builder host(String val) {