Adjust checkstyle rules. Make checkstyle fail the build when violations are found. Correct all current checkstyle violations.

lazy-loading/src/main/java/com/iluwatar/lazy/loading/HolderNaive.java

@@ -9,10 +9,16 @@ public class HolderNaive {
 
   private Heavy heavy;
 
+  /**
+   * Constructor
+   */
   public HolderNaive() {
     System.out.println("HolderNaive created");
   }
 
+  /**
+   * Get heavy object
+   */
   public Heavy getHeavy() {
     if (heavy == null) {
       heavy = new Heavy();