Clean up boolean email docs a bit

Author: oschwald

src/main/java/com/maxmind/minfraud/response/Email.java

@@ -58,15 +58,17 @@ public Boolean isDisposable() {
     /**
      * /**
      *
-     * @return True if the email address is for a free email service provider.
+     * @return Whether the email address is from a free email provider such as
+     * Gmail. If no email address was passed, this will be {@code null}.
      */
     @JsonProperty("is_free")
     public Boolean isFree() {
         return isFree;
     }
 
     /**
-     * @return True if the email address is associated with fraud.
+     * @return Whether the email address is associated with fraud. If no email
+     * address was passed, this will be {@code null}.
      */
     @JsonProperty("is_high_risk")
     public Boolean isHighRisk() {