added more convenience methods

src/main/java/org/kohsuke/github/GHPullRequest.java

@@ -76,6 +76,13 @@ public class GHPullRequest {
         return user;
     }
 
+    /**
+     * Repository to which the pull request was sent.
+     */
+    public GHRepository getRepository() {
+        return getBase().getRepository();
+    }
+
     /**
      * This points to where the change should be pulled into,
      * but I'm not really sure what exactly it means.