Added isValid() method.

src/main/java/com/messners/gitlab/api/models/Branch.java

@@ -36,4 +36,8 @@ public class Branch {
 	public void setProtected (Boolean isProtected) {
 		this.isProtected = isProtected;
 	}
+	
+	public static final boolean isValid (Branch branch) {
+		return (branch != null && branch.getName() != null);
+	}
 }

src/main/java/com/messners/gitlab/api/models/MergeRequest.java

@@ -107,4 +107,8 @@ public class MergeRequest {
 	public void setUpvotes (Integer upvotes) {
 		this.upvotes = upvotes;
 	}
+	
+	public static final boolean isValid (MergeRequest mergeRequest) {
+		return (mergeRequest != null && mergeRequest.getId() != null);
+	}
 }

src/main/java/com/messners/gitlab/api/models/Project.java

@@ -201,4 +201,8 @@ public class Project {
 	public void setWikiEnabled (Boolean wikiEnabled) {
 		this.wikiEnabled = wikiEnabled;
 	}
+	
+	public static final boolean isValid (Project project) {
+		return (project != null && project.getId() != null);
+	}
 }

src/main/java/com/messners/gitlab/api/models/User.java

@@ -163,4 +163,8 @@ public class User {
 	public void setWebsiteUrl (String websiteUrl) {
 		this.websiteUrl = websiteUrl;
 	}
+	
+	public static final boolean isValid (User user) {
+		return (user != null && user.getId() != null);
+	}
 }