Added created_at and updated_at fields.

src/main/java/org/gitlab4j/api/models/MergeRequest.java

 package org.gitlab4j.api.models;
 
+import java.util.Date;
 import java.util.List;
 
 import javax.xml.bind.annotation.XmlAccessType;
@@ -14,6 +15,7 @@ public class MergeRequest {
     private Assignee assignee;
     private Author author;
     private Changes changes;
+    private Date createdAt;
     private String description;
     private Integer downvotes;
     private Boolean forceRemoveSourceBranch;
@@ -35,6 +37,7 @@ public class MergeRequest {
     private String targetBranch;
     private Integer targetProjectId;
     private String title;
+    private Date updatedAt;
     private Integer upvotes;
     private Integer userNotesCount;
     private String webUrl;
@@ -72,6 +75,14 @@ public class MergeRequest {
         this.changes = changes;
     }
 
+    public Date getCreatedAt() {
+        return createdAt;
+    }
+
+    public void setCreatedAt(Date createdAt) {
+        this.createdAt = createdAt;
+    }
+
     public String getDescription() {
         return description;
     }
@@ -240,6 +251,14 @@ public class MergeRequest {
         this.title = title;
     }
 
+    public Date getUpdatedAt() {
+        return updatedAt;
+    }
+
+    public void setUpdatedAt(Date updatedAt) {
+        this.updatedAt = updatedAt;
+    }
+
     public Integer getUpvotes() {
         return upvotes;
     }

src/test/resources/org/gitlab4j/api/merge-request.json

@@ -8,6 +8,8 @@
     "state":"merged",
     "upvotes":0,
     "downvotes":0,
+    "created_at": "2016-12-03T17:23:34Z",
+    "updated_at": "2016-12-03T17:23:34Z",
     "author":{
         "id":1,
         "username": "admin",