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

state/src/main/java/com/iluwatar/state/App.java

@@ -13,6 +13,9 @@ package com.iluwatar.state;
  */
 public class App {
 
+  /**
+   * Program entry point
+   */
   public static void main(String[] args) {
 
     Mammoth mammoth = new Mammoth();

state/src/main/java/com/iluwatar/state/Mammoth.java

@@ -13,6 +13,9 @@ public class Mammoth {
     state = new PeacefulState(this);
   }
 
+  /**
+   * Makes time pass for the mammoth
+   */
   public void timePasses() {
     if (state.getClass().equals(PeacefulState.class)) {
       changeStateTo(new AngryState(this));