1211 Add description to public interface.

Author: Richard Blaylock

impl/src/main/java/com/stormpath/sdk/impl/oauth/OAuthStormpathFactorChallengeGrantAuthenticationAttempt.java

@@ -18,6 +18,9 @@
 import com.stormpath.sdk.resource.Resource;
 
 /**
+ * This class is used to wrap the information required to request an OAuth token in exchange for verifying
+ * a challenge to an authentication factor.
+ *
  * @since 1.3.1
  */
 public interface OAuthStormpathFactorChallengeGrantAuthenticationAttempt extends Resource {